Distance calculation short-circuited by typo

[xloem]

This line appears to have a critical typo in it:

HiddenEngrams/engram.py

Line 92 in bbcd480

if nodeup is None or nodeup < 0 or nodedown is None or nodedown:

The last condition, or nodedown, will be True for all but the first index.

What's the intended behavior here?

I notice a similar check is replicated in the block below it.

Elsewhere it was tried to comment this out and replace the previous/next indices with whole object references to resolve the resulting sorting issues in example.py.