[TASK] Added System.err output if an unknown argument is given

src/main/java/org/parabot/Landing.java

@@ -27,15 +27,14 @@ public final class Landing {
     private static String username;
     private static String password;
 
-
     public static void main(String... args) throws IOException {
 
-        if (Context.getJavaVersion() >= 9){
+        if (Context.getJavaVersion() >= 9) {
             UILog.log("Parabot", "Parabot doesn't support Java 9+ currently. Please downgrade to Java 8 to ensure Parabot is working correctly.");
             System.exit(0);
         }
 
-        if(!System.getProperty("os.arch").contains("64")) {
+        if (!System.getProperty("os.arch").contains("64")) {
             UILog.log("Parabot", "You are not running a 64-bit version of Java, this might cause the client to lag or crash unexpectedly.\r\n" +
                     "It's recommended to upgrade to a 64-bit version.");
         }
@@ -152,6 +151,9 @@ public final class Landing {
                 case "-uuid":
                     Core.setQuickLaunchByUuid(Integer.parseInt(args[++i]));
                     break;
+                default:
+                    System.err.println(String.format("Unknown argument given: %s", arg.toLowerCase()));
+                    break;
             }
         }
     }