I was able to reproduce this in 4.5 Preview. I also checked our internal build, and it looks like it has already been fixed. This should no longer cause a crash in 4.6, and I will see if the fix will make it into the 4.5 Release. Thanks for pointing this out!
For now, you are correct: Go to Next Tutorial Stage is causing the crash, and removing it should solve the problem for you. You probably shouldn’t be able to use that node there, as it is referencing something that is no longer open when the Tutorial Stage Ended event is called.