Merge pull request apache#76 from michal-narajowski/ias-cb-fix

nimble/host: Add check before calling a IAS event callback

Author: Michał Narajowski

nimble/host/services/ias/src/ble_svc_ias.c

@@ -103,8 +103,10 @@ ble_svc_ias_access(uint16_t conn_handle, uint16_t attr_handle,
                                    sizeof ble_svc_ias_alert_level,
                                    sizeof ble_svc_ias_alert_level,
                                    &ble_svc_ias_alert_level, NULL);
-        /* Call the IAS event function */
-        ble_svc_ias_cb_fn(ble_svc_ias_alert_level);
+	/* Call the IAS event function */
+	if (ble_svc_ias_cb_fn) {
+		ble_svc_ias_cb_fn(ble_svc_ias_alert_level);
+	}
         return rc;
 
     default: