Use empty string for comparison

lib/renderer/window-setup.js

@@ -80,7 +80,7 @@ module.exports = (ipcRenderer, guestInstanceId, openerId, hiddenPage) => {
 
   // Make the browser window or guest view emit "new-window" event.
   window.open = function (url, frameName, features) {
-    if (url != null && url.length > 0) {
+    if (url != null && url !== '') {
       url = resolveURL(url)
     }
     const guestId = ipcRenderer.sendSync('ELECTRON_GUEST_WINDOW_MANAGER_WINDOW_OPEN', url, frameName, features)