Whilst viewing a branch with staged/unstaged files, right click a file in the unstated area and choose Discard to throw away the changes.

The initial dialogue (Confirm Discard?) has OK/Cancel. Press [ENTER] as that is the default option.

New dialogue shown (Add/remove files). Has a Close option.

At this point you will notice that the Close and the Commit buttons (the commit button is behind the dialogue) are both "active".

Pressing [ENTER] and expecting Close to be acted (as the dialogue is in front), fails.

Pressing [ESCAPE] does nothing (very annoying - escape to dismiss dialogs with only 1 option is a perfectly reasonable approach).