Fixes #3234 AZBackgroundMediaFormatter breaks field displays on non-p…

…aragraph entities (#3235)

modules/custom/az_paragraphs/src/Plugin/Field/FieldFormatter/AZBackgroundMediaFormatter.php

@@ -430,7 +430,7 @@ protected function getAllSettings(FieldItemListInterface $items): array {
     $all_settings = [];
     // Paragraph instance settings override everything.
     $paragraph_settings = $this->getParagraphSettings($items);
-    $all_settings += $paragraph_settings['az_text_media_paragraph_behavior'];
+    $all_settings += $paragraph_settings['az_text_media_paragraph_behavior'] ?? [];
     // Field formatter settings.
     $all_settings += $this->getSettings();
     // Fill in all the rest of the required settings.