In this case we did nothing in the past, but we should delete the
reference in fact.

The problem was that when the symref is not packed but the referenced
ref is packed, then we assumed that the symref is packed as well, but
symrefs are never packed.
Signed-off-by: NMiklos Vajna <vmiklos@frugalware.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>