Issue #3465478 by dieterholvoet: 'Undefined array key "vid"' when adding views filter

src/Plugin/views/filter/TaxonomyEnumReference.php

@@ -60,17 +60,16 @@ class TaxonomyEnumReference extends ManyToOne {
       return $this->valueOptions;
     }
 
-    if (!$vid = $this->options['vid']) {
-      $this->valueOptions = [];
-      return;
+    if (empty($this->options['vid'])) {
+      return $this->valueOptions = [];
     }
 
+    $vid = $this->options['vid'];
     $vocabulary = $this->entityTypeManager->getStorage('taxonomy_vocabulary')->load($vid);
     $enumName = $vocabulary->getThirdPartySetting('taxonomy_enum', 'enum_name');
 
     if (!enum_exists($enumName) || !method_exists($enumName, 'from')) {
-      $this->valueOptions = [];
-      return;
+      return $this->valueOptions = [];
     }
 
     $termStorage = $this->entityTypeManager
@@ -81,7 +80,7 @@ class TaxonomyEnumReference extends ManyToOne {
       ->execute();
     $terms = $termStorage->loadMultiple($termIds);
 
-    $this->valueOptions = array_reduce(
+    return $this->valueOptions = array_reduce(
       $terms,
       function (?array $options, TermInterface $term) {
         $options[$term->get('machine_name')->value] = $term->label();
@@ -110,7 +109,7 @@ class TaxonomyEnumReference extends ManyToOne {
         },
         Vocabulary::loadMultiple(),
       ),
-      '#default_value' => $this->options['vid'],
+      '#default_value' => $this->options['vid'] ?? NULL,
     ];
   }