qcacmn: Add check to avoid NULL pointer deference in parse MBSSID

In malformed beacon frame may deference the NULL pointer while
parsing MBSSID IE in util_scan_parse_mbssid will lead to crash.

Add check in util_scan_parse_mbsssid for split_prof_start before
passing to util_gen_new_ie and assign zero to split_prof_len
whenever split_prof_start freed to avoid unanticipated scenario.

Change-Id: Ibb9739d6b5d1775ab52d59f9aa5050ca693cd926
CRs-Fixed: 3717571