msm: ipa: Fix KW P1 issue

KW tool detect the potential NULL access and buffer
index overflow issue.
The change is to add the proper handle for NULL response
and prevent buffer index overflow.

Change-Id: I0bb1b45ba6e5b0abe6c3539d451f74e19028737c
Signed-off-by: Bojun Pan <bojunp@codeaurora.org>