object-refs: avoid division by zero
object-refs: avoid division by zero

Currently, we don't check refs_hash_size size and happily call
lookup_object_refs() even if refs_hash_size is zero which leads to
a division by zero in hash_obj().

Signed-off-by: Andre Noll <4aaaf3c285f100eb4c3bf3318694b035bcec79c5@systemlinux.org>
Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git