TYPO3 Exception 1561583127

TYPO3 10.4.28 - 2020-05-25

Exception message:

InvalidArgumentException: TypoScriptFrontendController must be constructed with a valid SiteLanguage object or a resolved site in the current request as fallback. None given.

Situation

The Preview section of a flux content element used <f:cObject> to access a TypoScript-defined function. Because no TSFE is available in the backend, one is created and that brings this error

Solution

Workaround: Do not use <f:cObject> in backend previews.

In TYPO3v11 this has been fixed with https://forge.typo3.org/issues/91511, but that change has not been backported to v10.