Make setenvif terminate when it should, instead of by accident, and also

correctly handle multiple env vars to be set. As a side-effect, eliminate
an env var with a null name.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@80060 13f79535-47bb-0310-9956-ffa450edef68