prune: do not show error from pack-redundant when no packs are found.
prune: do not show error from pack-redundant when no packs are found.

When there is no pack yet, git-prune leaked an error message
from "git-pack-redundant --all" which complained that there is
no pack.  Squelch the annoying message.

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