Merge r331041 from trunk:

* Fix a null pointer dereference in dav_method_mkcol during the handling of
  errors from dav_auto_checkin.

Submitted by: Ghassan Misherghi <ghassanm ucdavis.edu>
Reviewed by: rpluem


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.0.x@371650 13f79535-47bb-0310-9956-ffa450edef68