fix(dismissable-layer): guard isTopMostLayer against empty layers array

[EduardF1]

Problem

isTopMostLayer crashes with TypeError when layers array is empty.

Root cause

layers[layers.length - 1].node throws when layers is empty, since layers[-1] is undefined. Can happen during teardown or before a layer is registered.

Fix

Add a length guard:

function isTopMostLayer(node: HTMLElement | null) {
  return layers.length > 0 && layers[layers.length - 1].node === node;
}
```n
Returning `false` for an empty stack is correct — no layer is on top.

Fixes #649

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🔨 Latest commit	7eadb77

[jer3m01]

Thanks for the fix! Will get this for release this week.

[EduardF1]

Summary

Adds a one-line defensive guard to isTopMostLayer to handle an empty layers array, fixing a crash that occurs after programmatically closing the last dismissable layer (fixes #649).

Status

• CI: ✅ No unresolved review threads
• Narrowly scoped — no behavior change in the happy path
• Ready for review

@jer3m01 happy to rebase or adjust the guard/test placement if needed. Thanks!

[EduardF1]

Thanks @jer3m01, appreciate it. If it helps before release, I can also add a tiny regression test around the empty-stack case, but I kept the patch minimal since the fix is just the defensive length guard.

[EduardF1]

@jer3m01 friendly check-in on the release timing for this. If a patch-version bump or a CHANGELOG entry would help unblock cutting it, happy to push that in a follow-up commit.

[EduardF1]

Hi team, gentle ping — CI is green and the change is small. Would appreciate a review when you get a chance! 🙏

[EduardF1]

Hi team, checking in on this PR! Let me know if you have any questions.