$dispatch event unexpectedly converts undefined to {}

[JohnTing]

I tested the following values, and only undefined was different from what I expected.

    <div x-data="{}">
        <div @test-event.window="console.log($event.detail )"></div>
        <button x-on:click="$dispatch('test-event', undefined)">Click me</button>
        <button x-on:click="$dispatch('test-event', null)">Click me</button>
        <button x-on:click="$dispatch('test-event', 1)">Click me</button>
        <button x-on:click="$dispatch('test-event', 'A')">Click me</button>
        <button x-on:click="$dispatch('test-event', {})">Click me</button>
    </div>

result

{}
null
1
A
{}