If edit the Article class to use the xmlexport features (activating the fields and the class for export) you cannot store the new class definitions, see attached image for error.

This was tested in mysqli (singlemode) and postgres dfs cluster

Testcases: tc-72 and tc-74

Steps to reproduce

1. Install the ezxmlexport extension
2. On Setup / Classes edit the Article class
3. Check the "Class available for XML export" field
4. Store the Class