msm: camera: Fixing NULL dereference in sensor code

Fixing issue where we are referring to a null pointer.
Changing the if condition so that it does not access
the varibale when it is null.

Change-Id: I2f96cd0d301f580c0e7019746bade4e125661a36
CRs-Fixed: 1076948
Signed-off-by: Samyukta Mogily <smogily@codeaurora.org>