Issue #3393008: Fix OptGroupEntityReferenceSelection::getReferenceableEntities() error

Issue #3393008: Fix OptGroupEntityReferenceSelection::getReferenceableEntities() error, and generally refactor function to use continue to move to the next element in foreach() loops so code is less indented.

Closes #3393008

src/Plugin/EntityReferenceSelection/OptGroupEntityReferenceSelection.php

@@ -61,18 +61,33 @@ class OptGroupEntityReferenceSelection extends TermSelection {
     $has_admin_access = $this->currentUser->hasPermission('administer taxonomy');
     $unpublished_terms = [];
     foreach ($bundle_names as $bundle) {
-      if ($vocabulary = Vocabulary::load($bundle)) {
-        /** @var \Drupal\taxonomy\TermInterface[] $terms */
-        if ($terms = $this->entityTypeManager->getStorage('taxonomy_term')->loadTree($vocabulary->id(), 0, NULL, TRUE)) {
-          foreach ($terms as $term) {
-            if (!$has_admin_access && (!$term->isPublished() || in_array($term->parent->target_id, $unpublished_terms))) {
-              $unpublished_terms[] = $term->id();
-              continue;
-            }
-            $label = Html::escape($this->entityRepository->getTranslationFromContext($term)->label());
-            if ($term->depth !== 0) {
-              $options[$vocabulary->id()][$parent][$term->id()] = str_repeat('-', $term->depth - 1) . $label;
-            }
+      if (($vocabulary = Vocabulary::load($bundle)) === NULL) {
+        // Couldn't load vocabulary, so move on to the target bundle.
+        continue;
+      }
+      $terms = $this->entityTypeManager->getStorage('taxonomy_term')->loadTree($vocabulary->id(), 0, NULL, TRUE);
+      if (!$terms) {
+        // No terms, so move on to the next target bundle.
+        continue;
+      }
+      $parent = NULL;
+      foreach ($terms as $term) {
+        // If there is a reason to not show this term...
+        if (!$has_admin_access && (!$term->isPublished() || in_array($term->parent->target_id, $unpublished_terms))) {
+          // ...add it to the list of unpublished terms and move on to the next
+          // term.
+          $unpublished_terms[] = $term->id();
+          continue;
+        }
+        $label = Html::escape($this->entityRepository->getTranslationFromContext($term)->label());
+        // If this is a top level term...
+        if ($term->depth === 0) {
+          // ...don't add it to the options, but use it
+          $parent = $label;
+        }
+        else {
+          if ($parent) {
+            $options[$vocabulary->id()][$parent][$term->id()] = str_repeat('-', $term->depth - 1) . $label;
           }
         }
       }