Do not show "data loss" dialog multiple times

[probonopd]

Maybe the easiest is to check for windows with the same title like this:

    if not normalized_drive.startswith("/tmp") and not os.path.basename(normalized_drive).startswith("."):
        dialog_title = f"Warning - {normalized_drive}"
        if not is_dialog_open(dialog_title):
            QtWidgets.QMessageBox.critical(
                None, dialog_title,
                f"Volume {normalized_drive} was removed without being ejected first.\n\n"
                "To prevent data loss, always eject volumes before removal."
            )