fix(backend): ensure internal notifications are created in a valid format (#10502) (#10506)

Closes #10435

(cherry picked from commit 96a5291766)

Co-authored-by: Matthias Mair <code@mjmair.com>

src/backend/InvenTree/plugin/builtin/integration/core_notifications.py

@@ -38,6 +38,10 @@ class InvenTreeUINotifications(NotificationMixin, InvenTreePlugin):
         if not users:
             return False
 
+        # Ensure that there is always target object - see https://github.com/inventree/InvenTree/issues/10435
+        if not target:
+            target = self.plugin_config()
+
         # Bulk create notification messages for all provided users
         for user in users:
             entries.append(