Weirdness in page breaking

[Geoff Horton]

2.6.4, Cygwin.

I was setting a score that fit fine on one page, but that had a blank
markup block below it (left over from the file I'd used as a template)
that went onto a second page. I deleted the markup, and the last line
of music moved onto the second page. This isn't a catastrophic
problem, but it is annoying.

Unfortunately, the file itself is too long to post here and it doesn't
boil down into a neat test case.