qcacmn: Avoid ml_ap_ctx access on STA vap

In scenario where mbssid is enabled (is_mbssid_enabled) on STA ML VAP,
if ML STA is trying to assoc to Non-ML AP, on freeing AID at the STA
ml_ap_ctx is referred which is not set for STA vap leading to null
pointer access.

Check for validity of ml_ap_ctx before access.

Change-Id: Ib8b924cfc035c1e3aeeb5154ef6d736aee6ba077
CRs-Fixed: 3357392

umac/mlo_mgr/src/wlan_mlo_mgr_aid.c

@@ -805,6 +805,9 @@ void mlme_free_aid(struct wlan_objmgr_vdev *vdev, uint16_t assoc_id)
 		return;
 	}
 
+	if (!ml_dev->ap_ctx)
+		return;
+
 	ml_aid_mgr = ml_dev->ap_ctx->ml_aid_mgr;
 	if (!ml_aid_mgr)
 		return;