Allow null values for serial.adapter. https://github.com/nurikk/z2m-frontend/issues/449

lib/util/settings.js

@@ -322,7 +322,7 @@ function applyEnvironmentVariables(settings) {
     const iterate = (obj, path) => {
         Object.keys(obj).forEach((key) => {
             if (key !== 'type') {
-                if (key !== 'properties') {
+                if (key !== 'properties' && obj[key]) {
                     const type = (obj[key].type || 'object').toString();
                     const envPart = path.reduce((acc, val) => `${acc}${val}_`, '');
                     const envVariableName = (`ZIGBEE2MQTT_CONFIG_${envPart}${key}`).toUpperCase();
@@ -347,7 +347,7 @@ function applyEnvironmentVariables(settings) {
                     }
                 }
 
-                if (typeof obj[key] === 'object') {
+                if (typeof obj[key] === 'object' && obj[key]) {
                     const newPath = [...path];
                     if (key !== 'properties') {
                         newPath.push(key);

lib/util/settings.schema.json

@@ -144,7 +144,7 @@
         },
         "adapter": {
           "type": ["string", "null"],
-          "enum": ["deconz", "zstack", "zigate", "ezsp"],
+          "enum": ["deconz", "zstack", "zigate", "ezsp", null],
           "title": "Adapter",
           "requiresRestart": true,
           "description": "Adapter type, not needed unless you are experiencing problems"