Remove the None case

src/documents/admin.py

@@ -44,7 +44,7 @@ class TagAdmin(GuardedModelAdmin, TreeNodeModelAdmin):
 
         # sync parent tags on documents if changed
         new_parent = obj.get_parent()
-        if old_parent != new_parent:
+        if new_parent and old_parent != new_parent:
             update_document_parent_tags(obj, new_parent)
 
 

src/documents/tasks.py

@@ -517,14 +517,11 @@ def check_scheduled_workflows():
                         )
 
 
-def update_document_parent_tags(tag: Tag, new_parent: Tag | None) -> None:
+def update_document_parent_tags(tag: Tag, new_parent: Tag) -> None:
     """
     When a tag's parent changes, ensure all documents containing the tag also have
     the parent tag (and its ancestors) applied.
     """
-    if new_parent is None:
-        return
-
     DocumentTagRelationship = Document.tags.through
 
     doc_ids: list[int] = list(

src/documents/views.py

@@ -346,7 +346,7 @@ class TagViewSet(ModelViewSet, PermissionsAwareDocumentCountMixin):
         old_parent = self.get_object().get_parent()
         tag = serializer.save()
         new_parent = tag.get_parent()
-        if old_parent != new_parent:
+        if new_parent and old_parent != new_parent:
             update_document_parent_tags(tag, new_parent)