Avoid a NULL-pointer dereference.
Avoid a NULL-pointer dereference.

Found by: Coverity <http://scan.coverity.com/>
(CID: 75)

* subversion/libsvn_subr/mergeinfo.c
  (combine_with_lastrange):  Allocate a stucture before attempting to
    access its members.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion