Update actions in the warnings menu.

def update_code_analysis_actions(self):
        """Update actions in the warnings menu."""
        editor = self.get_current_editor()
        # To fix an error at startup
        if editor is None:
            return
        results = editor.get_current_warnings()
        # Update code analysis buttons
        state = (self.get_option('code_analysis/pyflakes') \
                 or self.get_option('code_analysis/pep8')) \
                 and results is not None and len(results)
        for action in (self.warning_list_action, self.previous_warning_action,
                       self.next_warning_action):
            if state is not None:
                action.setEnabled(state)