platform: msm_shared: avb: perfrom NULL check

avb_descriptor_get_all function can return NULL.
Need to perform a NULL check before it get accessed.

Change-Id: I698a322d6ccde3b0fd5a75452dedb17eecc2faed
Signed-off-by: Firoz Khan <firozk@codeaurora.org>
1 file changed