OS/2: Returning an empty string from ap_os_case_canonical_filename() when

given an invalid file name just makes matters worse as nobody checks the
return value. In particular, directory_walk() barfs big time when it tries to
access index.html on a FAT partition (not 8.3 so invalid) as num_dirs can
become -1 in an unsigned int.....


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@86835 13f79535-47bb-0310-9956-ffa450edef68