ASoc: msm: qdsp6v2: Fix for NULL check

- Required check added for NULL pointer

CRs-fixed: 583939
Change-Id: I8b079c42ef06af9a817dc830c5f2d3c785232aa7
Signed-off-by: Mingming Yin <mingming@codeaurora.org>
Update Makefile
Fix unintialized and undefined vars being treated as errors with -O3