Merge r1471449 from trunk:

* Fix null pointer dereference in case SetEnvif and SetEnvIfExpr are used
  together.

PR: 54881

Submitted by: rpluem
Reviewed by: rpluem, covener, humbedooh


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1476143 13f79535-47bb-0310-9956-ffa450edef68