Fix CommandClient random response selector

lib/command/Command.js

@@ -123,7 +123,7 @@ class Command {
                     throw new Error("Invalid command response generator (index " + index + ")");
                 }
             });
-            this.execute = () => this.responses[Math.floor(Math.random() * this.responses.length)];
+            this.execute = () => this.responses[Math.floor(Math.random() * this.responses.length)]();
         } else if(typeof generator === "function") {
             this.execute = generator;
         } else {