*: handle PermissionError when saving files, ensure permission bits are set correctly

closes #3817

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

authentik/core/api/applications.py

@@ -232,7 +232,11 @@ class ApplicationViewSet(UsedByMixin, ModelViewSet):
             return Response({})
         if icon:
             app.meta_icon = icon
-            app.save()
+            try:
+                app.save()
+            except PermissionError as exc:
+                LOGGER.warning("Failed to save icon", exc=exc)
+                return HttpResponseBadRequest()
             return Response({})
         return HttpResponseBadRequest()