Follow-up to r1532866: make the de-serializer actually return
a pointer to the copy of the cache contents.

* subversion/libsvn_repos/dump.c
  (deserialize_node_kind): fix access violation

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1532879 13f79535-47bb-0310-9956-ffa450edef68