71df742eb4
One of the consequences of the mistake in 3fcf535d2e (fixed in previous
commit), was that the more recent `LIB_EMBEDDED_DATA_LIB_OVERRIDE` ID
flag could be wrongly set in some nodetrees from pre-2.76 blendfiles.
This commit adds a check that embedded IDs flagged with
`LIB_EMBEDDED_DATA_LIB_OVERRIDE` are actually embedded IDs of a
liboverride.
Pull Request: https://projects.blender.org/blender/blender/pulls/118921