In switch-case structure, `PROP_NEVER_NULL` is already set for String properties. However, the code setting `PROP_EDITABLE` below was overwriting the flag. Then `PROP_NEVER_NULL` had to be set for a second time. Fixed by using proper API function to set these flags, and removed the redundant second flag setting. Pull Request: https://projects.blender.org/blender/blender/pulls/113739