Unloading without finished causes crash

I've used the wrapper of stfy (stfy/react-editor.js) but I think the error is located inside editor.js.

When the editor is initializing - at a certain stage not in every stage - and I switch context to another tab [my way of context switch] the destroy method is fired, which seems ok. However when the observer is disconnected (this.observer.disconnect() in modificationObserver.ts) the disconnect method doesn't exists yet. Which causes an error.