If one tries to open a setting window, the emulator grabs the input.
However, if opening the window then fails (most commonly because it is
joystick settings window, and there are no online nor offline gamepads)
the grab needs to be undone because otherwise the grab will point to
freed memory. The destructor would undo it, except failure to open window
triggers exit from constructor by exception, in which case destructor
will not run.
Bug reported on IRC.
88160be520