Why am I getting "Empty message body"?

Empty Message Body.pptx
When I complete a transaction using Alphauserpoint it decuts the points and says so in a message box. Underneath I get an empty box with "Empty message body" written in it. Why? How do I get rid of that empty message box? I have sent print screens in PowerPoint attached.

BTW, I do not get the "Empty Message Body" when I do not allow Alphauserpoint to pay for shipping and I do not charge extra for shipping. So it seems to be related to shipping charge paid by Alphauserpoint.