create render fall inside an infinite loop

I try to build a straightforward svelte app with some code examples, but when I add a new link, my code will be stuck in rendering (or try to render) the graph.

This may be related to this exception that I see.

```
REE.BufferGeometry.computeBoundingSphere(): Computed radius is NaN. The "position" attribute is likely to have NaN values. TH
```

Any idea?

The repo, when you can reproduce it is there https://git.hedwing.dev/vincenzopalazzo/ngraph-svelte

Start by reproducing the issue with the linked ngraph-svelte example, especially after adding a new link, and inspect the graph rendering path around the reported THREE.BufferGeometry.computeBoundingSphere() exception. Done means identifying why rendering loops and produces NaN position values, then confirming that the example renders normally after the link is added.

Written by the indexing model from the issue text.