This patch fixes the error that pops up
(`Error: Unable to execute '... Mode Toggle', error changing modes`)
when trying to switch to e.g. draw mode from a grease pencil object
that was saved in draw mode in an inactive scene when the file was loaded.
Note that this does not fix the bigger issue described in T91243.
The fix makes sure that we reset all the mode flags on the grease pencil
data when we set the mode to object mode.
Reviewed By: antoniov
Maniphest Tasks: T89514
Differential Revision: https://developer.blender.org/D12419
e9150ac317