If an Object with Null value is assigned to AdditionalDataItems, then wrong error message is thrown.

Steps to regenerate

If you set any null value to AdditionalDataItems, then, an Error is thrown saying that there is a problem about WRITE permission, which is not actually the correct error message. Moreover, the user should be able to set null value to an additional data item which will be converted to an Empty String.
Please feel free to share your comment.