Fix a server SEGV when AuthzForceUsernameCase is used without authentication.
Fix a server SEGV when AuthzForceUsernameCase is used without
authentication.

* subversion/mod_authz_svn/mod_authz_svn.c
  (get_username_to_authorize): Allow NULL username.

Patch by: roderich.schupp{_AT_}googlemail.com


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1149572 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion