Works for closing, not for minimizing

[mdavis-xyz]

I'm using Ubuntu 16.04 with Cinnamon (not Unity).

The extension works perfectly when I close Thunderbird. However when I minimize the window, it minimizes like a normal application, instead of going to the tray.

I have tried setttings preferences to both "When minimizing" and "Instead of closing and when minimizing". Neither one results in minimization to tray.

[skaros]

Same for me under Ubuntu 16.04 Unity. It minimizes when closed or using the menu(File->minimize to tray) but not when minimized.

[sboekhoff]

Duplicate of #103