Missing in 0.29.2 notmuch-dump.c: Fix output file being closed twice

[Ralph Seichter]

* David Bremner:

> That push was pushed to master, but not release. I guess at the time
> it didn't seem serious enough to warrant a point release?

I did not expect a point release for that patch in particular. However,
given that the patch fixed a SIGABRT situation, I have assumed to see it
included in whatever release came next. Version 0.29.2 happens to be the
first release since the bugfix was accepted three months ago, hence my
moderate disappointment that the fix is missing.

-Ralph