src/Router.js
function notFound(state) {
    logger.log('State not found: {0}', state)

    if (options.notFound)
      return setState(leafStates[options.notFound], {})
    else throw new Error ('State "' + state + '" could not be found')
  }
function notFound(state) {
    logger.log('State not found: {0}', state)

    if (options.notFound)
      return setState(leafStates[options.notFound], {})
    else throw new Error ('State "' + state + '" could not be found')
  }
/*
The state wasn't found
Transition to the 'notFound' state if the developer specified it or else throw an error.