Spring RTS Engine

A little bug with the Show Build widget - it draws squares around building that are going to be built, but those squares remains even after the building has been completed.
The squares only dissappear when something else is queued to be built.

Can someone please fix it, or tell me how to fix it?

I tried reading the code, but I couldn't find what removes the squares. I fear that perhaps they are not removed by the widget at all. I'm too new to Lua and Spring's widgets to tell for sure.

Honestly, that widget is a real mess, and the task of keeping track of buildings is a fiddly one. If I was to fix it I would just start from scratch.

There are alternatives out there to showing allies buildings, like the 'Show Orders' widget, so unless you really need buildings shown all the time I'd just use that and save yourself some coding trouble (keeping track of buildings has a lot of bothersome special cases)