Fix a potential problem in merge. The code used a stack variable after it had gone
out of scope.

Found by the Clang compiler's Address Sanitizer.

* subversion/libsvn_client/merge.c
  (merge_locked): Tweak to avoid using a stack variable outside its scope.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1587946 13f79535-47bb-0310-9956-ffa450edef68