Comment 3 for bug 1787717

"(null)" _is_ the cache file name, so the parser is correct in reporting that it wrote that cache file ;-)

# ls -l /var/cache/apparmor/9b2cd0d0.0/*null*
-rw------- 1 root root 0 1. Jan 1970 /var/cache/apparmor/9b2cd0d0.0/(null)

(empty file because I only pressed Ctrl-D, but I can easily produce a non-empty "(null)" cache file by entering a valid profile via stdin)