* [NOD-1388] Write a deterministic test that reproduces the crash.
* [NOD-1388] Fix a typo.
* [NOD-1388] Use isInPastOfAny in addValidTip instead of just checking the parents.
* [NOD-1388] Add a json representation of the crashing DAG.
* [NOD-1388] Remove crash_test.go.
* [NOD-1388] Change variable name, add a comment.
* [NOD-1388] Rephrase a comment.