Camera2: fix possible NPE on configurationchange

Step to reproduce:
- open camera from lockscreen
- while it is opening turn your phone
- result: crash

Due that the camera is in middle of the initialization mParameters
is null at this point. Just check against null to prevend the crash.
The correct resizing happens so or so during the ongoing initialization

Change-Id: I0aab385172d7ff571adf525004305fd3b34d499c