LibJS: VERIFY() that property name is valid in Value::get{,_method}()

Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/a3c8ebd7097
Pull-request: https://github.com/SerenityOS/serenity/pull/8262
Reviewed-by: https://github.com/IdanHo
Reviewed-by: https://github.com/alimpfard ✅
Reviewed-by: https://github.com/awesomekling ✅
Reviewed-by: https://github.com/davidot
Reviewed-by: https://github.com/mattco98

Userland/Libraries/LibJS/Runtime/Value.cpp

@@ -799,6 +799,7 @@ Value Value::get(GlobalObject& global_object, PropertyName const& property_name)
     auto& vm = global_object.vm();
 
     // 1. Assert: IsPropertyKey(P) is true.
+    VERIFY(property_name.is_valid());
 
     // 2. Let O be ? ToObject(V).
     auto* object = to_object(global_object);
@@ -815,6 +816,7 @@ FunctionObject* Value::get_method(GlobalObject& global_object, PropertyName cons
     auto& vm = global_object.vm();
 
     // 1. Assert: IsPropertyKey(P) is true.
+    VERIFY(property_name.is_valid());
 
     // 2. Let func be ? GetV(V, P).
     auto function = get(global_object, property_name).value_or(js_undefined());