MongoDB 3.6 requires a cursor document in the aggregate command, even if the last stage is a $out. The driver currently never includes a cursor document in this situation, resulting in a server error being returned and an exception thrown. There is no workaround.

While this problem has been fixed in the 3.5 release as part of JAVA-2442, the commit for that includes an API change that is not appropriate for a patch release. This issue is tracking a backport of just the change required to fix $out.