Fix NPE in DesktopModeWindowDecor#setAnimatingTaskResizeOrReposition

setAnimatingTaskResizeOrReposition currently check if the viewHolder is
an instance of an AppHandleViewHolder, and, if so, returns. However,
this does not account in cases where the view holder is null (i.e. if
the app crashes before setAnimatingTaskResizeOrReposition is called).

Bug: 406515706
Test: drag to desktop
Flag: EXEMPT bugfix
Change-Id: Ibce8eba0eb8c45ee9d87c91a062c6a305cee7f78