Tiarra IRC Proxy: Avoid warnings for Slack IRC gateway

gistfile1.diff

--- a/main/IrcIO/Server.pm
+++ b/main/IrcIO/Server.pm
@@ -829,6 +829,9 @@ sub _MODE {
        };

        for (;$mode_char_pos < $n_params;$mode_char_pos += $mode_param_offset + 1) {
+           if (substr($msg->param($mode_char_pos), 0, 1) eq ' ') {
+               next;
+           }
            $mode_param_offset = 0; # これは毎回リセットする。
            foreach my $c (split //,$msg->param($mode_char_pos)) {
                my $add_or_delete = ($plus ? 'add' : 'delete');