a631dc5575
Caused by {rB3f3d82cfe9ce}
Since above commit, a `uiRNACollectionSearch` may contain a NULL
`search_prop`, crashing the menu entry for "Jump To Target"
(`ui_jump_to_target_button_poll`).
Now safeguard against this with a NULL check (getting search callbacks
to work for "Jump To Target" can be investigated in master).
Maniphest Tasks: T100731
Differential Revision: https://developer.blender.org/D15832