Add missing null check
Add missing null check

 Bug: 13635394
 mDisplayListData can be null, make sure
 to check for that before trying to walk through the
 children list in updateProperties

Change-Id: I8d97b1656c1acf47b7c5df8a8771b0f30907261d

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