fix: error caused by hair object deletion

[GixoXYZ]

System Information
Operating system: All

Blender Version
Broken: All
Worked: -

GBH Tool Version
Broken: 2.2.0.alpha.3
Worked: All Previous

Short description of error

"BlenderGBHTool\ui\common_ui.py", line 71, in clear_pointer_if_object_deleted
    setattr(prop_parent, prop_pointer, None)
AttributeError: Writing to ID classes in this context is not allowed: Scene, Scene datablock, error setting Scene.hair_object

Exact steps for others to reproduce the error
Remove the selected hair object manually from the viewport.

Additional context
clear_pointer_if_object_deleted function has been recently changed to be working with parent armature selection and this error is the result of that changes.