Update main.js

Fix duplicate handler problem on macos

main.js

@@ -11,6 +11,8 @@ const createWindow = () => {
             preload: path.join(__dirname, 'preload.js'),
         }
     })
+    // There can be only one handler so remove the previous one first
+    ipcMain.removeHandler('ping')
     ipcMain.handle('ping', () => 'pong')
     win.loadFile('index.html')
 }