Fix problem where closing an invalid file descriptor causes core

a coredump. Reported on Linux.
Reviewed by: Randy Terbush, Howard Fear
Submitted by: Howard Fear


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@76668 13f79535-47bb-0310-9956-ffa450edef68