commit-graph: fix memory leak when not writing graph
When write_commit_graph()
bails out writing a split commit-graph early
then it may happen that we have already gathered the set of existing
commit-graph file names without yet determining the new merged set of
files. This can result in a memory leak though because we only clear the
preimage of files when we have collected the postimage.
Fix this issue by dropping the condition altogether so that we always try to free both preimage and postimage filenames.
Signed-off-by: Patrick Steinhardt ps@pks.im