Fix regression in ListView click handling

Regression caused by patch a607223f

If an item click handler results in the ListView becoming detached
from the window, the performClick runnable could be executed twice.
Null out the mTouchModeReset runnable before running the click handler
so that it is not run by the detach handler.

Change-Id: I2fab60232027bb4876f9912088e0ffb9b17d308c