Javascript error after closing live preview pane; subsequent link editing is glitched

[croxton]

Description

When the Live Preview panel is closed, an Uncaught TypeError is thrown.

When you try to subsequently edit existing links within a Redactor field (with the preview pane closed), the context toolbar ('Edit link', 'Unlink') does not appear. There may be other effects as well once the error has been triggered - we have received reports that adding new links may cause existing links to disappear, when you have multiple Redactor fields in a Matrix field - but I have not been able to reproduce.

Uncaught TypeError: Cannot read property 'createDocumentFragment' of undefined
    at xe (jquery.js? [sm]:5004)
    at Re (jquery.js? [sm]:6073)
    at b.fn.init.append (jquery.js? [sm]:6264)
    at b.fn.init.b.each.b.fn.<computed> [as appendTo] (jquery.js? [sm]:6398)
    at Object.handler (RedactorOverrides.js:410)
    at s.constructor.trigger (garnish.js? [sm]:840)
    at s.constructor.close (Preview.js:385)
    at s.constructor.<anonymous> (garnish.js? [sm]:893)
    at HTMLButtonElement.o (jquery.js? [sm]:10771)
    at HTMLButtonElement.dispatch (jquery.js? [sm]:5429)

As you can see the error relates to this line:

redactor/src/assets/field/src/js/RedactorOverrides.js

Line 410 in baa0509

$(this.$contextbar.get()).appendTo($target.get(0));

Steps to reproduce

1. Create a Redactor field using the 'Default' config, and attach to a new Section with no other fields
2. Create a new entry and add a link to the Redactor field
3. Click 'Preview'
4. Close the 'Close Preview' button
5. Note that clicking the link you created no longer shows the contextual toolbar

Additional info

• Craft version: 3.6.0.1
• PHP version: 7.4.12
• Database driver & version: 5.7.12
• Plugins & versions: Redactor 2.8.5 (tested with no other plugins installed)

[croxton]

This seems to fix it:

var detachLivePreview = () => {
   var $target = this.toolbar.getTargetElement();
   if ($target.length) {
      $(this.$contextbar.get(0)).appendTo($target.get(0));
   }
   this.livePreview = false;
}