The fix for https://bugs.openjdk.org/browse/JDK-8363889 makes

PrintJob.getGraphics() always return a Graphics.
After PrintJob.end() is called it should return null.
This has been long-standing behavior even though it isn't specified.

This was missed because the test for this is not being run due to a bug in the test tag - it is a closed test for no very good reason.