Fix an assertion caused by running 'svn log <SOME_URL>@PREV'.

* subversion/libsvn_client/log.c
  (svn_client_log5): Use a flag to remember which flavor of paths the
    log targets are (URL or WC), consulting it later so we can call the
    appropriate svn_*_condense_targets() API.

Reported by: danielsh

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1462134 13f79535-47bb-0310-9956-ffa450edef68