block/block-copy: fix -Werror=maybe-uninitialized false-positive

../block/block-copy.c:591:12: error: ‘ret’ may be used uninitialized [-Werror=maybe-uninitialized]

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
1 file changed