Hi,

I was reading the source code of preact signals (https://github.com/preactjs/signals/blob/main/packages/core/src/index.ts) and I noticed a small redundancy in the code.

The condition node._source._version !== node._version appears twice in the if statement. I am not an expert, but I think, the second condition could be removed.

One more thing:

Typescript complains that head is of type undefined at line 498 (cleanUpSources func). I will just paste the error here:

index.ts|498 col 4-8 error| Type 'Node' is not assignable to type 'undefined'.

I think, an easy fix would be to make head have Node | undefined type.

I would be happy to make a pull request to fix these minor issues and contribute to open source for the first time (well, not really, I tried to contribute to a project but it didn't go well lol)