Improve robustness.

lib/controller.js

@@ -113,6 +113,7 @@ class Controller {
         const deviceID = Object.keys(settings.get().devices).find((id) => settings.get().devices[id].friendly_name === friendlyName);
         if (!deviceID) {
             logger.error(`Cannot handle '${topic}' because deviceID of '${friendlyName}' cannot be found`);
+            return;
         }
 
         // Convert the MQTT message to a Zigbee message.

lib/zigbee.js

@@ -103,6 +103,7 @@ class Zigbee {
         const device = this.shepherd.find(deviceID, 1);
         if (!device) {
             logger.error(`Zigbee cannot publish message to device because '${deviceID}' is not known by zigbee-shepherd`);
+            return;
         }
 
         logger.info(`Zigbee publish to '${deviceID}', ${cId} - ${cmd} - ${JSON.stringify(zclData)}`);