critical() is intended for critical/fatal errors that threaten the
overall stability of an application. A user entering a conflicting key
sequence is neither of those.
Without passing in a parent, this can result in focus being stolen from
the dialog in certain cases.
Example:
On Windows, if the logging window is left open, the logging Window will
potentially get focus over the hotkey dialog itself, since it brings all
open windows for the application into view. By specifying a parent, we
only bring windows for the parent into view (of which there are none,
aside from the hotkey dialog).
