Fix crash when play button is pressed twice

Tricky beast: if the `Play` button is pressed without recording something first, the playback will fail and the state will change to `STOPPED`. When `Play` is clicked again, it will try to seek to 0, and throw an exception because there is no media file. The exception is caught, but doesn't contain a message, which crashes `Log.d`.

The fix sets the state back to `IDLE` instead of `STOPPED`.