undefined index notice when adding "smartqueue"

Problem/Motivation

Steps to reproduce -- I've got Drupal 8.8.5 and Entityqueue 8.x-1.0-rc1.

1. Add a new entityqueue (/admin/structure/entityqueue/add)
2. Choose "smart queue" (the log messages at steps 8-9 aren't happening when I choose "simple queue").
3. When the next part of the form loads, choose "Content" (also happens with "taxonomy term" entity type).
4. Now, a "notice" is logged in watchdog:
   Type/Severity: php/notice
   Location: https://www.mysite.com/admin/structure/entityqueue/add?_wrapper_format=drupal_ajax&_wrapper_format=drupal_ajax&ajax_form=1
   Message: Notice: Undefined index: bundles in Drupal\entityqueue_smartqueue\Plugin\EntityQueueHandler\SmartQueue->buildConfigurationForm() (line 115 of /path/to/modules/contrib/entityqueue/modules/entityqueue_smartqueue/src/Plugin/EntityQueueHandler/SmartQueue.php)
   >> Stacktrace pasted below this list of steps.
5. When the next part of the form loads, I chose the content type I wanted.
6. Further down, I went to the "Entity settings" vertical tab.
7. Choose "Content" (I haven't tried choosing other entity types).
8. When the next part of the form loads, I choose a bundle.
9. Now, a "notice" is logged in watchdog -- same details as the last on, but the location doesn't have the "_wrapper_format" param, so it's just https://www.mysite.com/admin/structure/entityqueue/add?_wrapper_format=drupal_ajax&ajax_form=1 (message is identical).
10. Then, I choose a "sort by" value, and save the new entity queue.

Secondary thing: I *swear* the first two times I tried this process, the progress bar happened after I hit "save" on the new smart queue, but no subqueues were generated -- I edited the entity queue configuration, and the content type that I selected the first time wasn't selected, so I checked the box again, hit save, and then the subqueues were generated. But, trials 3, 4, 5, and 6 didn't have this problem, so, I'm sharing the info in this "secondary" comment, because is isn't as consistent -- but like, if I hadn't checked a box next to a content type, it wouldn't let me save the "add new entityqueue" form, b/c it's a required field... ANYWAY, just saying :)
UPDATE: I reproduced this "secondary" issue when I created smart queues for taxonomy terms -- when I created new smart queues for taxonomy terms, the subqueues were not generated. I configured the new entity queues, re-selected the vocabulary (no vocabs were selected when I went to configure the entity queue), saved, and the subqueues were generated. I did this twice, then I added a new smart queue from a third vocabulary, and this third time, the subqueues were properly generated from the terms in that vocab. It feels like it has to generate subqueues from two smart queues of an entity type (or just saving the bundle setting for two smart queues of an entity type) before gets the hang of generating subqueues for an entity type (or just saving the bundle setting on a smart queue for an entity type)... I know it sounds bizarre, but that's the behavior I'm seeing :-/
>> I don't know if this bug is related to the "undefined index" bug, but the log message seems to be about "bundles" and the bundle setting for the smart queue isn't getting saved, so it feels related??
>> There are *no* watchdog entries in dblog for this bug -- the only log messages I get are the ones I trigger with the ajax form fields, as described in the numbered steps above.

>> Stacktrace for PHP notice:

Notice: Undefined index: bundles in Drupal\entityqueue_smartqueue\Plugin\EntityQueueHandler\SmartQueue->buildConfigurationForm() (line 115 of /path/to/web/modules/contrib/entityqueue/modules/entityqueue_smartqueue/src/Plugin/EntityQueueHandler/SmartQueue.php)

#0 /path/to/web/core/includes/bootstrap.inc(600): _drupal_error_handler_real(8, 'Undefined index...', 'path/to...', 115, Array)
#1 /path/to/web/modules/contrib/entityqueue/modules/entityqueue_smartqueue/src/Plugin/EntityQueueHandler/SmartQueue.php(115): _drupal_error_handler(8, 'Undefined index...', 'path/to...', 115, Array)
#2 /path/to/web/modules/contrib/entityqueue/src/Form/EntityQueueForm.php(150): Drupal\entityqueue_smartqueue\Plugin\EntityQueueHandler\SmartQueue->buildConfigurationForm(Array, Object(Drupal\Core\Form\SubformState))
#3 /path/to/web/core/lib/Drupal/Core/Entity/EntityForm.php(149): Drupal\entityqueue\Form\EntityQueueForm->form(Array, Object(Drupal\Core\Form\FormState))
#4 [internal function]: Drupal\Core\Entity\EntityForm->buildForm(Array, Object(Drupal\Core\Form\FormState))
#5 /path/to/web/core/lib/Drupal/Core/Form/FormBuilder.php(520): call_user_func_array(Array, Array)
#6 /path/to/web/core/lib/Drupal/Core/Form/FormBuilder.php(370): Drupal\Core\Form\FormBuilder->retrieveForm('entity_queue_ad...', Object(Drupal\Core\Form\FormState))
#7 /path/to/web/core/lib/Drupal/Core/Form/FormBuilder.php(627): Drupal\Core\Form\FormBuilder->rebuildForm('entity_queue_ad...', Object(Drupal\Core\Form\FormState), Array)
#8 /path/to/web/core/lib/Drupal/Core/Form/FormBuilder.php(320): Drupal\Core\Form\FormBuilder->processForm('entity_queue_ad...', Array, Object(Drupal\Core\Form\FormState))
#9 /path/to/web/core/lib/Drupal/Core/Controller/FormController.php(91): Drupal\Core\Form\FormBuilder->buildForm(Object(Drupal\entityqueue\Form\EntityQueueForm), Object(Drupal\Core\Form\FormState))
#10 [internal function]: Drupal\Core\Controller\FormController->getContentResult(Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\RouteMatch))
#11 /path/to/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array)
#12 /path/to/web/core/lib/Drupal/Core/Render/Renderer.php(573): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#13 /path/to/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure))
#14 /path/to/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array)
#15 /path/to/vendor/symfony/http-kernel/HttpKernel.php(151): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#16 /path/to/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)
#17 /path/to/web/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#18 /path/to/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#19 /path/to/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(106): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#20 /path/to/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#21 /path/to/web/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#22 /path/to/web/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(52): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#23 /path/to/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#24 /path/to/web/core/lib/Drupal/Core/DrupalKernel.php(708): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#25 /path/to/web/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request))
#26 {main}

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Original report by [username]

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