The issue is that `DOM_WINDOW_DESTROYED_TOPIC` is advertised when the JavaScript is still running, so it runs on a partially unlinked object (via `::Observe` instead of cycle collection). That is being removed in bug 1811882.
Bug 1835390 Comment 4 Edit History
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The issue is that `DOM_WINDOW_DESTROYED_TOPIC` is advertised when the JavaScript is still running, so it runs on a partially unlinked object (via `::Observe` instead of cycle collection). That observer is being removed in bug 1811882.