Uncaught CKEditorError: collection-add-item-invalid-index - missing cancel button

Problem/Motivation

This is likely the same issue in 🐛 Exceptions thrown when toggling Advanced section of linking form Active but I cannot reopen that one.

When "open in a new window" is not enabled as an option, a JS exception is thrown, and the cancel button is not displayed in the link dialog.

Steps to reproduce

Configure the text format to use some elements of advanced link but not open in a new window.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes