Mandatory/required image field does not validate

Image fields that are mandatory/required are not validated. You can leave the field empty/blank and will still be able to save/publish the document.

Reproducible in latest go-green (2.24.00).
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This issues was fixed as part of CMS7-6810 on both trunk(2.24.xx) and branch (2.22.xx), but it is working only on trunk. So I cloned this issue from former.