do not save some parameter of config which is invalid

main/config.js

@@ -35,7 +35,9 @@ let config = {
     y: userSettingsStore.get('y'),
     maximized: !!userSettingsStore.get('maximized'),
     save: function (item) {
-        userSettingsStore.set(item, this[item]);
+        if (item && this[item] != undefined) {
+            userSettingsStore.set(item, this[item]);
+        }
     }
 };
 

main/main.js

@@ -202,10 +202,18 @@ app.on('ready', () => {
     core.mainWindow.on('closed', () => {
         try {
             if (!config.maximized) {
-                config.save('width');
-                config.save('height');
-                config.save('x');
-                config.save('y');
+                if (config.width > 0) {
+                    config.save('width');
+                }
+
+                if (config.height > 0) {
+                    config.save('height');
+                }
+
+                if (config.x > 0 && config.y > 0) {
+                    config.save('x');
+                    config.save('y');
+                }
             }
 
             config.save('maximized');