LibJS: break or continue with nonexistent label is a syntax error

Author: https://github.com/mattco98
Commit: e8da5f99b1
Pull-request: https://github.com/SerenityOS/serenity/pull/3724
Issue: https://github.com/SerenityOS/serenity/issues/3714
Reviewed-by: https://github.com/linusg

Libraries/LibJS/Tests/break-continue-syntax-errors.js

@@ -2,8 +2,7 @@ test("'break' syntax errors", () => {
     expect("break").not.toEval();
     expect("break label").not.toEval();
     expect("{ break }").not.toEval();
-    // FIXME: Parser does not throw error on nonexistent label
-    // expect("{ break label }.not.toEval();
+    expect("{ break label }").not.toEval();
     expect("label: { break label }").toEval();
 });