fixes detection whether last argument is a username or not

src/trigger/umode.js

@@ -12,7 +12,7 @@ module.exports = (bot, trigger, lib) => {
       var tmp = e.message.trim().split(' ');
       tmp.shift();
       var user = tmp[tmp.length - 1];
-      if(user.match(/(\+|-)/))
+      if(!(user in e.channel.names))
         user = e.user.getNick();
       else
         tmp.pop();