Behavior of #each destructure with trailing commas

[GrygrFlzr]

Is your feature request related to a problem? Please describe.
Currently, when destructuring in an #each block with a trailing comma like this:

{#each list as {first, last, }}

The following error is spit out:

Not implemented Empty

(see this repl for an example)

Describe the solution you'd like
Allow for comma trails when destructuring in an #each block. This is consistent with JS object destructure notation, which supports this:

let obj = {x: 1, y: 2};
let {
  x,
  y,
} = obj;
console.log(x, y); // prints "1 2"

Describe alternatives you've considered
Have a clearer error message explaining that trailing commas are not supported. The current Not implemented Empty can lead to some hair-tearing situations, even if svelte decides to not support trailing commas in #each blocks.

How important is this feature to you?
Minor priority.

Additional context
This was brought up in the discord after someone encountered this particular issue.

[GrygrFlzr]

Also notable, in SSR mode a similarly vague error is produced:

Cannot read property '0' of null

[Conduitry]

This would be fixed by #4596 but unfortunately that PR needs a little more work because of changes that have happened in master in the meantime.

[Conduitry]

This works in 3.22.3 now - https://svelte.dev/repl/a81891adba51446daae8b2741b937cf2?version=3.22.3