Bugfix: using Image.GetCurrent() and image.save() on the "Render Result" image could result in a segfault since image->ibuf was NULL. This change forces ibuf to be created if necessary. NOTE: the Image API needs additional methods/attributes for image.save() to really do anything useful. The image type, quality, etc., don't seem to be gettable/settable so the resulting image file may not be in the format the user would like.