msm: camera: Handling get buf properly when buffer queue is empty

There can be a possibility that the buffer queue is empty and
we ask for a buffer. In that case the address holding the buffer queue
structure data is not NULL but the entries of the structure are
NULL.

In such a case in addition to checking if bufq address is NULL,
when we request for a buffer, we also make sure that handle is
not NULL.

CRs-Fixed: 533384

Change-Id: I78acdc0455cd187e709722a36d9943af0444eaee
Signed-off-by: Aditya Jonnalagadda <ajonnala@codeaurora.org>