qcacmn: Fix kw issue in target_if_nan_deregister_events

Potential NULL pointer dereference of handle in
target_if_nan_deregister_events. Add null check
in the function.

Change-Id: Ie30720b525c457e6c805bd0d212044be9270bd53
CRs-Fixed: 2323349

target_if/nan/src/target_if_nan.c

@@ -766,6 +766,10 @@ QDF_STATUS target_if_nan_deregister_events(struct wlan_objmgr_psoc *psoc)
 	int ret, status = 0;
 	wmi_unified_t handle = get_wmi_unified_hdl_from_psoc(psoc);
 
+	if (!handle) {
+		target_if_err("handle is NULL");
+		return QDF_STATUS_E_FAILURE;
+	}
 	ret = wmi_unified_unregister_event_handler(handle,
 				wmi_ndl_schedule_update_event_id);
 	if (ret) {