http-push: reuse existing is_null_ref
http-push: reuse existing is_null_ref

Signed-off-by: Clemens Buchacher <3561697699be488d2983f82b126a1881ffc3afbc@aon.at>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

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