The page will freeze permanently if I deserialize an empty (or invalid) FGB file with the specified rect.
There are no errors in the console.
sample file

let iter = flatgeobuf.ol.deserialize(url, rect);
for await (let _feature of iter) {...}

If I deserialize this file without specifying rect, then there are no problems.

const response = await fetch(url);
for await (let _feature of flatgeobuf.ol.deserialize(response.body)) {...}

But in this case the whole file is downloaded. I don't like it.
Now I use additional API to determine the file size. If the file is small then I use deserialize without Rect otherwise with Rect.

Originally posted by @voknez in #429