Caused by {rB1a81d268a19f}.
This caused e.g. ALT-clicking the 'Link' button to not propagate to
other selected objects (same as the 'Copy To Selected' context menu
entry).
If these are not unique across IDs, checks in ui_selectcontext_begin()
or copy_to_selected_button() could fail.
Now offset by ID pointer.
thx @JacquesLucke for clarification on the POINTER_* macros (and why
not to use them)!
Maniphest Tasks: T90907
Differential Revision: https://developer.blender.org/D12321
6845aad1a2