Fix dragging the same app over a split app dismisses the split

Do not evict splitting children if the app start animation was canceled.
So it won't apply the evict transaction which empties the split.

Fix: 219139163
Test: manual check dropping the same app on the same side of the split
      won't dismiss the split.
Change-Id: I5a450e53d857813f4fd59ab157be7d36985673ea