qcacmn: NULL pointer dereference in htc_issue_packets()

Inside htc_issue_packets() if the HTC frame header
associated with a packet is NULL, a NULL pointer dereference
can occur.

Add check to verify that HTC frame header is not NULL before
dereferencing.

Change-Id: I4169035286b582a91e5963c20a11c8ad0f375d17
Crs-Fixed: 2232846