From f33eb3f678c24c0b0b34ea27bcf6b14923c721af Mon Sep 17 00:00:00 2001
From: Andy Butland <abutland73@gmail.com>
Date: Mon, 27 Oct 2025 13:42:48 +0100
Subject: [PATCH] Media types: Handle null configured file extensions when
 populating allowed media types (closes #20620) (#20635)

* Handle null configured file extensions when populating allowed media types.

* Added clarifying comment.
---
 .../Services/ContentTypeEditing/MediaTypeEditingService.cs      | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Umbraco.Core/Services/ContentTypeEditing/MediaTypeEditingService.cs b/src/Umbraco.Core/Services/ContentTypeEditing/MediaTypeEditingService.cs
index 8a626215b4..4955eeec9c 100644
--- a/src/Umbraco.Core/Services/ContentTypeEditing/MediaTypeEditingService.cs
+++ b/src/Umbraco.Core/Services/ContentTypeEditing/MediaTypeEditingService.cs
@@ -175,7 +175,7 @@ internal sealed class MediaTypeEditingService : ContentTypeEditingServiceBase<IM
                 continue;
             }
 
-            allowedFileExtensionsByMediaType[mediaType] = fileUploadConfiguration.FileExtensions;
+            allowedFileExtensionsByMediaType[mediaType] = fileUploadConfiguration.FileExtensions ?? []; // Although we never expect null here, legacy data type configuration did allow it.
         }
 
         return allowedFileExtensionsByMediaType;