Drop close-without-saving confirmation dialog
If you close a Bustle window, you get a scary warning about losing the log you just recorded forever.
On the one hand, this is generally unnecessary: anecdotally, most users do not want to save their logs, they just want to record them and read them. On the other hand, it's also not true: all the logs are kept forever in $XDG_CACHE_DIR (#7).
Let's just drop this dialog.