More minor window mode fixes

Fixes #93.  The new window modes aren't perfect (and never will be!),
but they're getting better and better.  As I wrote in #98, I'm going to
move my focus onto improving little niggles as I find them, rather than
focusing exclusively on window mode stuff.

As such, I think it's safe to reinstate nightly builds, so I'll be doing
that following this commit!