Fix NPE while dispatching input event.
Fix NPE while dispatching input event.

- occasionally, TvView can be detached while
  the input event is being processed.

BUG: 14791903
Change-Id: Id1def32ace1bf9765ae30a00ea4579670d1d40aa

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base