Improve MQTT switch support.

lib/controller.js

@@ -156,7 +156,14 @@ class Controller {
         }
 
         // Convert the MQTT message to a Zigbee message.
-        const json = JSON.parse(message);
+        let json = null;
+        try {
+            json = JSON.parse(message);
+        } catch (e) {
+            // Cannot be parsed to JSON, assume state message.
+            json = {state: message.toString()};
+        }
+
         Object.keys(json).forEach((key) => {
             // Find converter for this key.
             const converter = mqtt2zigbee[key];

lib/converters/zigbee2mqtt.js

@@ -195,7 +195,7 @@ const parsers = [
         devices: ['ZNCZ02LM'],
         cid: 'genOnOff',
         type: 'attReport',
-        convert: (msg) => {return {state: msg.data.data['onOff'] === 1 ? '{"state": "ON"}': '{"state": "OFF"}'}}
+        convert: (msg) => {return {state: msg.data.data['onOff'] === 1 ? "ON" : "OFF"}}
     },
     {
         devices: ['ZNCZ02LM'],

lib/homeassistant.js

@@ -122,8 +122,8 @@ const homeassistant = {
         type: 'switch',
         object_id: 'switch',
         discovery_payload: {
-            payload_off: '{"state": "OFF"}',
-            payload_on: '{"state": "ON"}',
+            payload_off: 'OFF',
+            payload_on: 'ON',
             value_template: '{{ value_json.state }}',
             command_topic: true
         }