TYPO3 Core

Hello TYPO3-Team,

currently i get this error when i go to the first page of a submenu.

(1/1) #1476107295 TYPO3\CMS\Core\Error\Exception

PHP Warning: Undefined array key "prev" in /var/www/html/public/typo3/sysext/frontend/Classes/ContentObject/Menu/AbstractMenuContentObject.php line 1063
in /var/www/html/public/typo3/sysext/core/Classes/Error/ErrorHandler.php line 137

I'm using this menu dataprocessor:

page.10.dataProcessing {
    ## Main Menu
    10 = TYPO3\CMS\Frontend\DataProcessing\MenuProcessor
    10 {
        as = mainMenu
        expandAll = 1
        excludeUidList = {$mypackage.excludePagesMainMenu}
        levels = 3
        titleField = title // nav_title
    }
}

Many thanks
Steffen