Apparently if we are unable to parse an object update-server-info
coredumps, as it doesn't bother to check the return value of its
call to parse_object.
Instead of coredumping, skip the ref.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org> Signed-off-by: Junio C Hamano <junkio@cox.net>