Unable to close BBB meeting when started from desktop app

[cadavre]

If we click "Join meeting" from Mattermost desktop app and BBB meeting opens in browser window – after-call redirect (/plugins/bigbluebutton/redirect) cannot close the window due to JS restriction error:

Scripts may close only the windows that were opened by it.

This is due to:

<script>
  window.onload = function load() {
    window.open('', '_self', '');
    window.close();
  };
</script>

Browser: Chrome 78.

We could potentially provide an option for custom redirect instead of window.close() – it would be better to land on given URL instead of see empty page with JS console error.