The "Toggle Fullscreen" key bind doesn't work when set to a mouse button

Note: This is not a duplicate of MC-301791. This report describes a new issue.

Steps to reproduce:

1. Bind the toggle fullscreen key to mouse buttons like Button 5.

2. Try to use Button 5 in game.

Expected result:

The fullscreen mode will be toggled.

Actual result:

Nothing will happen.