"Empty return" plugin takes up Menubar space instead of disappearing - ex: showing only when some app is running

[ventz]

Noticed that "empty return" plugins take up Menubar space.

As an example - a plugin which shows the current playing track info Spotify and refreshes every N seconds. When you close Spotify, it should disappear from the Menubar (it does with BitBar).

Here is an example with xbar: