In Servers > Apache Webserver > MIME Types, the first
"Add a new MIME type" link doesn't work. The GET
variable, "file" is empty. The second link (at the
bottom of the page) has the "file" variable set with
the path to the mime.types file.
I get the same results if I use the "Default" option or
specify my own path to the file (in both cases, I tried
/usr/local/apache2/conf/mime.types, the file does exist
as I've confirmed it, editing MIME-types work as does
adding if done through the second link).
I fixed this on my installation by copying the code in
/path/to/webmin/apache/edit_global.cgi that determines
the file (lines 35 to 39) and pasting them under line
27 and then commenting out lines 35-39.
This seems to work both for "Default" and a specified file.
I've attached the edited file.