Fix missing content for listmaster admin template edits in the web interface

[racke]

This is a simple commit to fix the issue. The code for do_editfile could be improved further. Especially the following code doesn't make sense as it is called after the file contents have been slurped:

  if (-f $param->{'filepath'} && (!-r $param->{'filepath'})) {
        Sympa::WWW::Report::reject_report_web('intern', 'cannot_read',
            {'filepath' => $param->{'filepath'}},
            $param->{'action'}, '', $param->{'user'}{'email'}, $robot);
        wwslog('err', 'Cannot read %s', $param->{'filepath'});
        web_db_log(
            {   'parameters' => $in{'file'},
                'status'     => 'error',
                'error_type' => 'internal'
            }
        );
        return undef;
    }