InlineControlContainer disrespects GeneralUtility::callUserFunction's signature
The variable `$customControlConfig` is an array:
GeneralUtility::callUserFunction however expects its first argument to be a string or a function but not an array:
This breaks the `customControls` feature of inline-Fields in TCA as documented here: https://docs.typo3.org/typo3cms/TCAReference/8.7/ColumnsConfig/Type/Inline.html#customcontrols
Instead of passing an array of arrays as requested by the docs, one could just pass an array of functions and/or function identifiers to work around this issue.
Tested with TYPO3 versions 8 and 9.