Property accessed before initialization

Problem/Motivation

Error: Typed property Drupal\themespace\Plugin\Discovery\ProviderTypedAttributeClassDiscovery::$rootNsIterator must not be accessed before initialization in Drupal\themespace\Plugin\Discovery\ProviderTypedAttributeClassDiscovery->getPluginNamespaces() (line 194 of modules/contrib/themespace/src/Plugin/Discovery/ProviderTypedAttributeClassDiscovery.php).

Drupal\Component\Plugin\Discovery\AttributeClassDiscovery->__construct() (Line: 72)
Drupal\themespace\Plugin\Discovery\ProviderTypedAttributeClassDiscovery->__construct() (Line: 83)
Drupal\transmuter\Plugin\TransmuterManager->getDiscovery() (Line: 245)
Drupal\transmuter\Plugin\TransmuterManager->findTypedDefinitions() (Line: 99)
Drupal\transmuter\Plugin\TransmuterManager->findDefinitions() (Line: 216)
Drupal\Core\Plugin\DefaultPluginManager->getDefinitions() (Line: 280)
Drupal\transmuter\Plugin\TransmuterManager->groupPluginDefinitions() (Line: 304)
Drupal\transmuter\Plugin\TransmuterManager->getModuleDefinitions() (Line: 44)
Drupal\transmuter\ThemeRegistryBuilder->alterRegistry() (Line: 32)
transmuter_theme_registry_alter() (Line: 460)
Drupal\Core\Extension\ModuleHandler->alter() (Line: 491)
Drupal\Core\Theme\Registry->build() (Line: 326)
Drupal\Core\Theme\Registry->get() (Line: 90)
Drupal\Core\Utility\ThemeRegistry->initializeRegistry() (Line: 71)
Drupal\Core\Utility\ThemeRegistry->__construct() (Line: 368)
Drupal\Core\Theme\Registry->getRuntime() (Line: 139)
Drupal\Core\Theme\ThemeManager->render() (Line: 500)
Drupal\Core\Render\Renderer->doRender() (Line: 230)
Drupal\Core\Render\Renderer->render() (Line: 242)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 634)
Drupal\Core\Render\Renderer::Drupal\Core\Render\{closure}()
Fiber->resume() (Line: 649)
Drupal\Core\Render\Renderer->executeInRenderContext() (Line: 235)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare() (Line: 131)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse() (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray() (Line: 246)
Symfony\Component\EventDispatcher\EventDispatcher::Symfony\Component\EventDispatcher\{closure}() (Line: 206)
Symfony\Component\EventDispatcher\EventDispatcher->callListeners() (Line: 56)
Symfony\Component\EventDispatcher\EventDispatcher->dispatch() (Line: 188)
Symfony\Component\HttpKernel\HttpKernel->handleRaw() (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle() (Line: 53)
Drupal\Core\StackMiddleware\Session->handle() (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle() (Line: 32)
Drupal\big_pipe\StackMiddleware\ContentLength->handle() (Line: 118)
Drupal\page_cache\StackMiddleware\PageCache->pass() (Line: 92)
Drupal\page_cache\StackMiddleware\PageCache->handle() (Line: 50)
Drupal\ban\BanMiddleware->handle() (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle() (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle() (Line: 53)
Drupal\Core\StackMiddleware\AjaxPageState->handle() (Line: 54)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle() (Line: 745)
Drupal\Core\DrupalKernel->handle() (Line: 19)

Also happens for `$nsSuffixes`.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes