Update form-engine.js initializeLocalizationStateSelector

[s-leger]

function initializeLocalizationStateSelector
expression if (void 0 === t) fails when t is null.
When translating pages type link to subpages, t is null. (void 0 === t) fails to identify null values for t, leading to t.disabled errors.

[TYPO3IncTeam]

Thank you for your contribution to TYPO3. We are using Gerrit Code Review for our contributions and took the liberty to convert your pull request to a review in our review system.
You can find your patch at: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79406
For further information on how to contribute have a look at https://docs.typo3.org/typo3cms/ContributionWorkflowGuide/