[fix] runtime: destroy missing fragment

[TorstenDittmann]

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• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests

• Run the tests with npm test and lint the project with npm run lint

Problem

When manually removing a HTML element from a component, it is trying to be accessed later on in the destroy lifecycle where it throws an error.

This PR adds optional chaining before accessing removeChild from the parentNode property to prevent the error thrown.

I prepared a REPL where this fails => https://svelte.dev/repl/0d826c0d67c54d8693aeaa1b77ea09ef?version=3.44.2

[Conduitry]

There's (at least) one other PR for this already (#6910) but I'm not convinced this is something that we want to do.

[martinmogusu]

There's (at least) one other PR for this already (#6910) but I'm not convinced this is something that we want to do.

@Conduitry why would this not be a desirable change in your opinion? What is your suggested workaround?

I encountered a similar issue when trying to use the list.js package in Svelte. The package usually removes some nodes when filtering/searching and Svelte is not aware of the changes