[BUG] Console error in browser when opening PageContentAdmin

[jrief]

Description

I'm experiencing this error in the console of the browser:

Note that I bundled the client code using gulp bundle --debug to obtain more verbose information.

Steps to reproduce

• Open the page tree.
• Chose a page which is published, ie. having a green bullet.
• Click on the PageContent editor (button with 3 sliders).

Expected behaviour

No error in the browser console.

Actual behaviour

Browser reports: window.CMS.Widgets._pageSmartLinkWidgets is undefined.

Side note:

All the fields of that page's editor are readonly. If I open the editor of a page which is not published, then the editor opens with all the fields, but editable. Then this error does not occur.

Additional information (CMS/Python/Django versions)

Branch develop-4 current HEAD (92a1086decd082f1645e73bf6c8ab4d501b0e194)

Do you want to help fix this issue?

• [ ] Yes, I want to help fix this issue and I will join #workgroup-pr-review on Slack to confirm with the community that a PR is welcome.
• [x] No, I only want to report the issue.

Since I'm not aware of the purpose of this, I probably can't fix this myself.

[fsbraun]

@jrief Can you check if #7880 solves your issue?