Fix NDK CameraManager crash when no cameras exist

The NDK CameraManager only lists cameras that support camera API v2. For
a device that only supports v1 the list comes back empty. This results
in allocating an array of size zero. This array was then intialized with
a nullptr. This is fine if the array contains at least one item but in
the case where there are no cameras this will cause a buffer overflow.
This change removes the initialization which fixes the crash.

Test: manual - ran camera CTS tests
Change-Id: Ie1c872ff66997d55572fd855f20b56bd58b01752