Check result handler is not null
Check result handler is not null

If caller passes a null result handler to the proxy methods, we need
to check it when getting the result. Otherwise we try to invoke a method
on a null object

Change-Id: Ic2f456c36cb542b782b6a6d0d4d607ccf0987496

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