Ignore geometry parent when !useTasksDimOnly

ag/28428783 accidentally introduced a regression on the old unflagged
code

Bug: 366132859
Test: manual, verify bug is fixed when flag off
Flag: EXEMPT fix for old code not protected by com.android.window.flags.use_tasks_dim_only
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:93849f0b3027c83641e439ba7b41e1bb3e888e0d)
Merged-In: Ifb788c9cdbdfbafff0f784dcb4eb77595d73ff2a
Change-Id: Ifb788c9cdbdfbafff0f784dcb4eb77595d73ff2a