Cannot navigate back from player details

If you are on the [player list page](http://bitballs.herokuapp.com/players) and choose a player, then try to go back, it does not work. Due to minification, the stack trace is mostly useless, though.

```
Uncaught TypeError: Cannot read property 'id' of undefined
at a.id (index.js:7)
at a.getData (index.js:12)
at a.getData (index.js:12)
at a.get (index.js:11)
at a.get (index.js:11)
at Function.eval [as get] (index.js:11)
at p.get playerPromise (details.js:2)
at r.start (index.js:3)
at r.update (index.js:3)
at Object.r.updateAndNotify (index.js:3)
```

Reproduce the failure by opening the player list, selecting a player, and navigating back. Start with the minified stack references in index.js and details.js, then trace the playerPromise lookup; done means back navigation returns to the player list without the undefined-id error.

Written by the indexing model from the issue text.