Variable exists without creation. Next.js Bug

Can someone explain how is this possible?
How can I console.log(Konva) without defining or importing it?
Here we can see output
It is create-next-app.

export default function Sketch() {
    console.log(Konva);
    return <> <div>Empty</div> </>;
}

Output

{_global: Window, version: '8.3.12', isBrowser: true, isUnminified: true, dblClickWindow: 400, …}

Note if I'm trying to do the same in other file I will get Error Konva is not defined.