TYPO3 Core

I am using the "l10nmgr" extension in combination with custom Content Elements using FlexForms. Since Typo Version 6.2.10, I get the following warning:

Core: Error handler (BE): PHP Warning: Parameter 5 to tx_l10nmgr_tools::translationDetails_flexFormCallBackForOverlay() expected to be a reference, value given in /domains/www.test.local/typo3_src/typo3_src-6.2.13/typo3/sysext/core/Classes/Configuration/FlexForm/FlexFormTools.php line 242

The warning appears when the l10nmgr-Extension is installed and you save any record using FlexForms.

When I use the 6.2.9 source, everything is working fine. I saw, that there were changes in the FlexFormTools.php from 6.2.9 to 6.2.10. I had already a conversation with the develops of the l10nmgr, but they they it's an typo3 core bug.