Wrapper: Ensure Request max_content returns None

- Otherwise returns property object for else logic
- Safe handling of key/app existence

flask/wrappers.py

@@ -145,8 +145,7 @@ class Request(RequestBase, JSONMixin):
     @property
     def max_content_length(self):
         """Read-only view of the ``MAX_CONTENT_LENGTH`` config key."""
-        if current_app:
-            return current_app.config['MAX_CONTENT_LENGTH']
+        return current_app.config.get('MAX_CONTENT_LENGTH') if current_app else None:
 
     @property
     def endpoint(self):