qcacld-3.0: Fix possible null pointer dereference

roam_info may be null pointer and be explicitly
dereferenced when roam_status is
eCSR_ROAM_LOSTLINK in hdd_dis_connect_hanler.
Add null check for roam_info before
getting roam_info->reasonCode.

Change-Id: I11be7b722921a9be8ed1419251f6cbf19506a11d
CRs-Fixed: 2531563
1 file changed