TypeError: Cannot read property 'length' of undefined

[oldrich-svec]

monaco-editor version: 0.23.0
Browser: Google Chrome Version 87.0.4280.88 (Official Build) (64-bit)
OS: Windows 10
Playground code that reproduces the issue:

Navigate to:

https://microsoft.github.io/monaco-editor/playground.html

Paste:

const origText = `
/// <reference path="./x.d.ts" />

// @ts-ignore
const x
`
var originalModel = monaco.editor.createModel(origText, "typescript");
var modifiedModel = monaco.editor.createModel(``, "typescript");

var diffEditor = monaco.editor.createDiffEditor(document.getElementById("container"));

diffEditor.setModel({
	original: originalModel,
	modified: modifiedModel
});

gives