Fix only instantiate default property once

Author: gilzoide

src/script-language/LuaScriptInstance.cpp

@@ -97,7 +97,9 @@ GDExtensionBool get_func(LuaScriptInstance *p_instance, const StringName *p_name
 
 	// d) fallback to default property value, if there is one
 	if (property) {
-		*p_value = property->instantiate_default_value();
+		Variant value = property->instantiate_default_value();
+		p_instance->data->rawset(*p_name, value);
+		*p_value = value;
 		return true;
 	}
 

test/gdscript_tests/test_class.gd

@@ -27,7 +27,9 @@ func test_signal() -> bool:
 
 func test_array_properties() -> bool:
 	var obj = test_class.new()
+	var empty_array = obj.empty_array
 	assert(obj.empty_array == [])
+	assert(is_same(empty_array, obj.empty_array))
 	assert(!is_same(obj.empty_array, test_class.get_property_default_value("empty_array")), "Properties should be duplicated on instantiation")
 	assert(obj.preinitialized_array == [1, 2, 3])
 	assert(!is_same(obj.preinitialized_array, test_class.get_property_default_value("preinitialized_array")), "Properties should be duplicated on instantiation")