NPE in AcitivtyChooserModel.

1. If there is not current intent sent and the client tries to
   choose an activity a NPE occurs. The code in chooseActivity
   now checks for null intent. Note that having a null intent
   is a valid state.

bug:6738922

Change-Id: I91d4415649ce070d4fa4aa187e9eac02928dd38c
1 file changed