We print the number of commits in parentheses, but without this change
we would get an oddly looking line like this:

    * sm1 4c8d358...41fbea9 (      4):
Signed-off-by: NJohannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>