Fix undefined error when some dropdowns aren't shown in the images index view (#9211)

Fixes #9210

CHANGELOG.txt

@@ -53,6 +53,7 @@ Changelog
  * Fix: Update alignment and reveal logic of fields’ comment buttons (Steven Steinwand)
  * Fix: Regression from Markdown conversion in documentation for API configuration - update to correctly use PEP-8 for example code (Storm Heg)
  * Fix: Prevent 'Delete' link on page edit view from redirecting back to the deleted page (LB (Ben) Johnston)
+ * Fix: Prevent JS error on images index view when collections dropdown is omitted (Tidiane Dia)
 
 
 4.0.1 (05.09.2022)

docs/releases/4.0.2.md

@@ -28,3 +28,4 @@ depth: 1
  * Update alignment and reveal logic of fields’ comment buttons (Steven Steinwand)
  * Regression from Markdown conversion in documentation for API configuration - update to correctly use PEP-8 for example code (Storm Heg)
  * Prevent 'Delete' link on page edit view from redirecting back to the deleted page (LB (Ben) Johnston)
+ * Prevent JS error on images index view when collections dropdown is omitted (Tidiane Dia)

wagtail/images/templates/wagtailimages/images/index.html

@@ -15,9 +15,9 @@
 
         const submitFormOnDropdownChange = (dropdownSelector) => {
             const dropdown = document.querySelector(dropdownSelector);
-            dropdown.addEventListener('change', () => {
-                dropdown.form.submit();
-            })
+            if (dropdown !== null) {
+                dropdown.addEventListener('change', () => dropdown.form.submit());
+            }
         };
         const dropdownSelectors = [
             "#collection_chooser_collection_id",