Fix return statement in CanvasItem::get_global_transform_with_canvas

Thanks to @susnux for the report and patch in #5446.

scene/2d/canvas_item.cpp

@@ -339,6 +339,8 @@ Matrix32 CanvasItem::get_global_transform_with_canvas() const {
 		return last_valid->canvas_layer->get_transform() * xform;
 	else if (is_inside_tree())
 		return get_viewport()->get_canvas_transform() * xform;
+
+	return xform;
 }
 
 Matrix32 CanvasItem::get_global_transform() const {