Fix a core dump in mod_cache when it attemtped to store uncopyable
buckets. This happened, for instance, when a file to be cached
contained SSI tags to execute a CGI script (passed as a pipe
bucket). [Paul J. Reder]


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@97058 13f79535-47bb-0310-9956-ffa450edef68