Thanks for the report. I was able to reproduce this and I’ll be investigating further. I’ll post back here once it’s complete. It will likely be after the holiday here.
Sorry for the delay. I created JIRA UE-39144 for this crash and our developers will be investigating further. Please follow that link to monitor the bugs status and feel free to vote.
As for it locking you out of the project; try deleting the blueprint from your OS’s content browser. That should allow you to at least reopen the project.
PS : if you have an Add Point in your construction script and you saved, you are bound to crash on reopening the blueprint.
This ought to be a top priority issue.