Pasting list with empty bullet point from Google Docs causes Uncaught TypeError: Cannot read property 'is' of undefined

[tomi-bigpi]

📝 Provide detailed reproduction steps (if any)

1. Create a Google Doc with a bullet or numbered list with an empty bullet point, such as:

• Item 1

2. Copy the list onto the clipboard.
3. Paste into CKEditor (https://ckeditor.com/docs/ckeditor5/latest/features/pasting/paste-from-google-docs.html).

✔️ Expected result

Content is pasted into document.

❌ Actual result

No content is pasted and the following error shows up in the Console:

Uncaught TypeError: Cannot read property 'is' of undefined
    at list.js:96
    at u.execute (googledocsnormalizer.js:49)
    at u.t.plugins.get.on.priority (pastefromoffice.js:68)
    at u.fire (emittermixin.js:209)
    at a.listenTo.priority (clipboard.js:80)
    at a.fire (emittermixin.js:209)
    at a.n (clipboardobserver.js:51)
    at a.fire (emittermixin.js:209)
    at a.fire (domeventobserver.js:96)
    at a.onDomEvent (clipboardobserver.js:74)

📃 Other details

• Browser: Chrome 84.0.4147.135
• OS: macOS
• CKEditor version: 5
• Installed CKEditor plugins: PasteFromOffice

---

The issues is on line:

ckeditor5/packages/ckeditor5-paste-from-office/src/filters/list.js

Line 96 in ef3a8ad

if ( firstChild.is( 'element', 'p' ) ) {

It is missing a null check for firstChild, e.g.

			if ( firstChild && firstChild.is( 'element', 'p' ) ) {