Route for workflow_transition configuration field entity missing

Re-open with detailed steps to reproduce:

1. fresh install of drupal 8.2.4
   
   profile: standard, language: English
2. enable configuration translation core module
   
   will also enable interface translation and language modules
3. download and install workflow 8.x-1.0-beta6
4. enable workflow and workflow_ui
5. create a test workflow
   
   at /admin/config/workflow/workflow/add with default configuration
6. add some states, like progress / done
   
   at /admin/config/workflow/workflow/test/states
7. define some transions, eg. to author
   
   at /admin/config/workflow/workflow/test/transition_roles
8. create a workflow state field for the Test workflow on page content type
   
   at /admin/structure/types/manage/page/fields/add-field
9. try to uninstall the workflow_ui module (not the main workflow module)
   
   at /admin/modules/uninstall

you'll get "The website encountered an unexpected error. Please try again later."

Message on logs:

Error: Call to a member function getPath() on null in /var/www/html/core/modules/config_translation/src/ConfigNamesMapper.php on line 233

Backtrace:

Error: Call to a member function getPath() on null in /var/www/html/core/modules/config_translation/src/ConfigNamesMapper.php on line 233  #0 /var/www/html/core/modules/config_translation/src/Routing/RouteSubscriber.php(39): Drupal\config_translation\ConfigNamesMapper->getOverviewRoute() 
  #1 /var/www/html/core/lib/Drupal/Core/Routing/RouteSubscriberBase.php(37): Drupal\config_translation\Routing\RouteSubscriber->alterRoutes(Object(Symfony\Component\Routing\RouteCollection)) 
  #2 /var/www/html/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php(111): Drupal\Core\Routing\RouteSubscriberBase->onAlterRoutes(Object(Drupal\Core\Routing\RouteBuildEvent), 'routing.route_a...', Object(Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher)) 
  #3 /var/www/html/core/lib/Drupal/Core/Routing/RouteBuilder.php(184): Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch('routing.route_a...', Object(Drupal\Core\Routing\RouteBuildEvent)) 
  #4 /var/www/html/core/lib/Drupal/Core/ProxyClass/Routing/RouteBuilder.php(83): Drupal\Core\Routing\RouteBuilder->rebuild() 
  #5 /var/www/html/core/lib/Drupal/Core/Extension/ModuleInstaller.php(473): Drupal\Core\ProxyClass\Routing\RouteBuilder->rebuild() 
  #6 /var/www/html/core/lib/Drupal/Core/ProxyClass/Extension/ModuleInstaller.php(91): Drupal\Core\Extension\ModuleInstaller->uninstall(Array, true) 
  #7 /var/www/html/core/modules/system/src/Form/ModulesUninstallConfirmForm.php(160): Drupal\Core\ProxyClass\Extension\ModuleInstaller->uninstall(Array) 
  #8 [internal function]: Drupal\system\Form\ModulesUninstallConfirmForm->submitForm(Array, Object(Drupal\Core\Form\FormState)) 
  #9 /var/www/html/core/lib/Drupal/Core/Form/FormSubmitter.php(111): call_user_func_array(Array, Array) 
  #10 /var/www/html/core/lib/Drupal/Core/Form/FormSubmitter.php(51): Drupal\Core\Form\FormSubmitter->executeSubmitHandlers(Array, Object(Drupal\Core\Form\FormState)) 
  #11 /var/www/html/core/lib/Drupal/Core/Form/FormBuilder.php(585): Drupal\Core\Form\FormSubmitter->doSubmitForm(Array, Object(Drupal\Core\Form\FormState)) 
  #12 /var/www/html/core/lib/Drupal/Core/Form/FormBuilder.php(314): Drupal\Core\Form\FormBuilder->processForm('system_modules_...', Array, Object(Drupal\Core\Form\FormState)) 
  #13 /var/www/html/core/lib/Drupal/Core/Controller/FormController.php(74): Drupal\Core\Form\FormBuilder->buildForm('system_modules_...', Object(Drupal\Core\Form\FormState)) 
  #14 [internal function]: Drupal\Core\Controller\FormController->getContentResult(Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\RouteMatch)) 
  #15 /var/www/html/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array) 
  #16 /var/www/html/core/lib/Drupal/Core/Render/Renderer.php(574): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() 
  #17 /var/www/html/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure)) 
  #18 /var/www/html/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) 
  #19 [internal function]: Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() 
  #20 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(139): call_user_func_array(Object(Closure), Array) 
  #21 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(62): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1) 
  #22 /var/www/html/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
  #23 /var/www/html/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
  #24 /var/www/html/core/modules/page_cache/src/StackMiddleware/PageCache.php(99): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
  #25 /var/www/html/core/modules/page_cache/src/StackMiddleware/PageCache.php(78): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
  #26 /var/www/html/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
  #27 /var/www/html/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(50): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
  #28 /var/www/html/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\ 
 egotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
  #29 /var/www/html/core/lib/Drupal/Core/DrupalKernel.php(652): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) 
  #30 /var/www/html/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request))

This happen on every installation operation where workflow and related modules are involved, like configuration import in staging.

Tested version beta6

For me, the main problem here is that this bug breaks the configuration import. This forced me to get a temporary solution, patching the core config_translation module as follows:

diff --git a/core/modules/config_translation/src/Routing/RouteSubscriber.php b/core/modules/config_translation/src/Routing/RouteSubscriber.php
index b20c13f..da8480a 100644
--- a/core/modules/config_translation/src/Routing/RouteSubscriber.php
+++ b/core/modules/config_translation/src/Routing/RouteSubscriber.php
@@ -36,6 +36,13 @@ protected function alterRoutes(RouteCollection $collection) {
     $mappers = $this->mapperManager->getMappers($collection);
 
     foreach ($mappers as $mapper) {
+      // Temporary workaround for #2823659
+      if (
+        $mapper->getBaseRouteName() == 'entity.field_config.workflow_transition_field_edit_form' || 
+        $mapper->getBaseRouteName() == 'entity.workflow_type.edit_form'
+      ) {
+        continue;
+      }
       $collection->add($mapper->getOverviewRouteName(), $mapper->getOverviewRoute());
       $collection->add($mapper->getAddRouteName(), $mapper->getAddRoute());
       $collection->add($mapper->getEditRouteName(), $mapper->getEditRoute());

*not as an attachment because this is not a patch for the workflow module.

@johnv The error occurred while importing settings using drush on a new deployment. Workflow_ui was enabled, but I suspect the workflow module was installed by the config manager before the workflow_ui to satisfy some dependencies.

Another simpler scenario in which this bug occurs. Download and enable workflow_ui module for the first time. The main workflow module will be requested as a dependency. Working with drush, Drupal 8.3.7 & workflow 8.x-dev (8.x-1.0-beta6+29-dev):

# drush dl --dev workflow
Project workflow (8.x-1.x-dev) downloaded to /app/modules/workflow.                                                                                                                      [success]
Project workflow contains 7 modules: workflow_devel, workflow_ui, workflow_cleanup, workflow_access, workflowfield, workflow_operations, workflow.
# drush en workflow_ui
The following extensions will be enabled: workflow_ui, workflow
Do you really want to continue? (y/n): y
Error: Call to a member function getPath() on null in /app/core/modules/config_translation/src/ConfigNamesMapper.php on line 233 #0 /app/core/modules/config_translation/src/Routing/RouteSubscriber.php(39): Drupal\config_translation\ConfigNamesMapper->getOverviewRoute()
...

I can confirm that the bug, as described in #17, does not exist in latest -dev (tested on 8.4.0 core):

# drush en -y workflow_ui
The following extensions will be enabled: workflow_ui, workflow
Do you really want to continue? (y/n): y
workflow was enabled successfully.                                                                                    [ok]
workflow defines the following permissions: administer workflow
workflow_ui was enabled successfully.                                                                                 [ok]
Thanks for using Workflow. To maintain workflows,                                                                     [status]
    install the Workflow UI module. To start using
    a Workflow, add a Workflow Field to your entity.
Please review which roles may 'participate in workflows'                                                              [status]

Thank's