fetch: don't redundantly NULL something calloc() gave us

Stop redundantly NULL-ing the last element of the refs structure, which was retrieved via calloc(), and is thus guaranteed to be pre-NULL'd. This code dates back to b888d61c83 ("Make fetch a builtin", 2007-09-10), where wasn't any reason to do this back then either, it's just boilerplate left over from when git-fetch was initially introduced. The motivation for this change was to make a subsequent change which would also modify the refs variable smaller, since it won't have to copy this redundant "NULL the last + 1 item" pattern. We may not end up keeping that change, but as this pattern is still pointless, so let's fix it. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>