Update the regex text for the shortcut finder.

def set_regex(self, regex=None, reset=False):
        """Update the regex text for the shortcut finder."""
        if reset:
            text = ''
        else:
            text = self.finder.text().replace(' ', '').lower()

        self.proxy_model.set_filter(text)
        self.source_model.update_search_letters(text)
        self.sortByColumn(SEARCH_SCORE, Qt.AscendingOrder)

        if self.last_regex != regex:
            self.selectRow(0)
        self.last_regex = regex