Remove .unwrap() in detach()

[ronanM]

In a web crawler, when I strip the HTML tree, sometimes detach() panic on the .unwrap().

[LoZack19]

Detatch panics in three situations:

1. If its parent doesn't have any children (impossible)
2. If it's the first and not only child of its parent, but it doesn't have a next sibling (impossible)
3. If it's the last and not only child of its parent, but it doesn't have a previous sibling (impossible)

If detach went wrong, you must have a malformed tree. Could you point out which line of the detach method causes panic? I would also like a debug print of the tree you're using, in order to understand what is going wrong. If you provide us with more information, we could try to understand what part of the source code is failing.

Removing the unwrap isn't a solution, because if detatch fails, it means that there's something very wrong going on with the tree, and we must fix it. Some invariants must not be respected for this to happen.