qcacmn: Add null check for DP MLD context

Add NULL check in CDP API for MLD context as it can
be called by upper layers for non-MLO VAPs

Change-Id: Id77284ca81462a7e799a7b93e3528d9d9144372c
CRs-Fixed: 3605323

dp/wifi3.0/be/mlo/dp_mlo.c

@@ -670,7 +670,7 @@ static QDF_STATUS dp_mlo_get_mld_vdev_stats(struct cdp_soc_t *soc_hdl,
 		return QDF_STATUS_E_FAILURE;
 
 	vdev_be = dp_get_be_vdev_from_dp_vdev(vdev);
-	if (!vdev_be) {
+	if (!vdev_be || !vdev_be->mlo_dev_ctxt) {
 		dp_vdev_unref_delete(soc, vdev, DP_MOD_ID_GENERIC_STATS);
 		return QDF_STATUS_E_FAILURE;
 	}