retryTransition( route ) {
		const transition = get( this, "previousTransition" );

		if ( !transition ) {
			return route
				? this.transitionToRoute( route )
				: Promise.resolve();
		}

		set( this, "previousTransition", null );
		return transition.retry();
	}
Retry a previously stored transition
@param {string?} route
@returns {Promise}