@legocoder It isn't a problem with your code; it is a problem on Vivaldi's end, so no need to worry about it.
Vivaldi is sort of an app/extension on top of the Chromium core, so some extension aspect of the browser that is being injected is probably responsible for the error.
If you inspect the user interface, you will see multiple instances of that error in the console. Thanks to the developers for bringing that error to regular webpage consoles as well! Wouldn't want us modders to have all the fun with such an exciting feature... ๐