Notice: Undefined index: #id in template_preprocess_paragraphs_add_dialog__categorized()

Problem/Motivation

Upon insert of a new paragraph from the off-canvas dialog, a php notice is shown for Undefined index: #id in template_preprocess_paragraphs_add_dialog__categorized()

Steps to reproduce

Enable error display in the site.
In a paragraphs field with the following Paragraphs Experimental form widget settings:

• Title: Paragraph
• Plural title: Paragraphs
• Edit mode: Closed
• Closed mode: Summary
• Autocollapse: All
• Add mode: Modal form
• Form display mode: default
• Features: Duplicate, Collapse / Edit all, Add above
• Use off-canvas dialog
• Display paragraphs in dialog as: List
• Number of easy-access-buttons: 2

Click the "triple dot" control provided by Paragraphs Features.
Choose a paragraph.
Observe the following

 Notice: Undefined index: #id in template_preprocess_paragraphs_add_dialog__categorized() (line 294 of /var/www/docroot/modules/contrib/paragraphs_ee/paragraphs_ee.module). =>
array:24 [▼
  "23: template_preprocess_paragraphs_add_dialog__categorized()" => array:2 [▶]
  "22: Drupal\Core\Theme\ThemeManager->render()" => array:2 [▶]
  "21: Drupal\Core\Render\Renderer->doRender()" => array:2 [▶]
  "20: Drupal\Core\Render\Renderer->doRender()" => array:2 [▶]
  "19: Drupal\Core\Render\Renderer->render()" => array:2 [▶]
  "18: Drupal\Core\Render\Renderer->Drupal\Core\Render\{closure}()" => array:1 [▶]
  "17: Drupal\Core\Render\Renderer->executeInRenderContext()" => array:2 [▶]
  "16: Drupal\Core\Render\Renderer->renderRoot()" => array:2 [▶]
  "15: Drupal\Core\Render\MainContent\OffCanvasRenderer->renderResponse()" => array:2 [▶]
  "14: Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray()" => array:2 [▶]
  "13: call_user_func()" => array:1 [▶]
  "12: Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch()" => array:2 [▶]
  "11: Symfony\Component\HttpKernel\HttpKernel->handleRaw()" => array:2 [▶]
  "10: Symfony\Component\HttpKernel\HttpKernel->handle()" => array:2 [▶]
  " 9: Drupal\simple_oauth\HttpMiddleware\BasicAuthSwap->handle()" => array:2 [▶]
  " 8: Drupal\Core\StackMiddleware\Session->handle()" => array:2 [▶]
  " 7: Drupal\Core\StackMiddleware\KernelPreHandle->handle()" => array:2 [▶]
  " 6: Drupal\page_cache\StackMiddleware\PageCache->pass()" => array:2 [▶]
  " 5: Drupal\page_cache\StackMiddleware\PageCache->handle()" => array:2 [▶]
  " 4: Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle()" => array:2 [▶]
  " 3: Drupal\Core\StackMiddleware\NegotiationMiddleware->handle()" => array:2 [▶]
  " 2: Stack\StackedHttpKernel->handle()" => array:2 [▶]
  " 1: Drupal\Core\DrupalKernel->handle()" => array:2 [▶]
  " 0: main()" => array:2 [▶]
]

Proposed resolution

Use a conditional expression to build the id string.

Remaining tasks

None

User interface changes

None

API changes

None to our knowledge

Data model changes

None to our knowledge.