Holding a modifier when Catfish loses focus disables right-click
If the Catfish main window loses focus when a modifier (Control or Shift) is being pressed, the value is not removed from self.keys_pressed
when returning.
This causes the right click menu not to show on results until a modifier is pressed again.
Noticed this after finding/fixing the same bug in !55 (when using a modifier to open the Open dialog). It seems a really unlikely thing to happen under normal circumstances but just thought I'd add it here.