[541] Fix for returning a stale error pointer
During the rendering process (or Service_DrawObjectRender for unknown objects) the render state may be updated with an error pointer. However, as rending proceeds and potentially many other SWIs are called also using MessageTrans' shared buffers, by the end of the rendering process the originally captured pointer may be pointing at a totally different message. Capture the error after each object is despatched in our own buffer.