Fix the crash in AnimatorManager.

If we have >1 mAnimators and also the animator target changes,
`onAnimatorTargetChanged` function will erase mAnimators vector, while
in AnimatorManager::pushStaging, the process still does the loop for
mAnimators. Thus the crash happens.

Bug: 327666562
Test: n/a
Change-Id: I928185a2654b49660e226dcc89a2bc116cec870f