I feel like we could get into trouble with this somehow. Maybe `if title != ''` is cleaner? Or better yet:
```
if `filenames` in raw.info:
    title = raw.info['filenames'][0]
else:
    title = ''
```
I don't particularly like the idea of not having any window title, either. Maybe we could default to `<unknown>` or `raw plot` or something. We could also allow the user to pass in a title...?