correct harmless off-by-one mistake

a gc can only take place if we have at least three files - the current
file (which we cannot gc), the source file and the destination
file. We do a quick check wether there is enough data - garbage or
otherwise - to require more than two files. This can give false
positives since the last message in a file can overrun the
limit, but that's ok as the code that follows performs more accurate
(but also more expensive) checks.

0 files changed, 0 insertions, 0 deletions