Generating diff of this object for undo because the type tree changed still occurs.

I have attached a repro. Open the project. Navigate to the Locales directory and select one of the assets. In the inspector click the + icon for the Metadata and add a Comment, the error will be thrown and Undo will not work correctly.

Note: Also unable to apply changes made to prefab of Monobehaviours with SerializedReference objects. Tested on 2019.3.0f4 (91ed33c208f3)