Internal Server Error

exception 'DTS\eBaySDK\Exceptions\InvalidPropertyTypeException' with message 'Invalid property type provided for categoryId. Expected string but got NULL' in /www/htdocs/w0104af9/wundr-shop.de/ebay-sdk-php/DTS/eBaySDK/Types/RepeatableType.php:178
Stack trace:
#0 /www/htdocs/w0104af9/wundr-shop.de/ebay-sdk-php/DTS/eBaySDK/Types/RepeatableType.php(84): DTS\eBaySDK\Types\RepeatableType->ensurePropertyType(NULL)
#1 /www/htdocs/w0104af9/wundr-shop.de/ebay-sdk-php/DTS/eBaySDK/Types/BaseType.php(374): DTS\eBaySDK\Types\RepeatableType->offsetSet(NULL, NULL)
#2 /www/htdocs/w0104af9/wundr-shop.de/ebay-sdk-php/DTS/eBaySDK/Types/BaseType.php(301): DTS\eBaySDK\Types\BaseType->setValue('DTS\\eBaySDK\\Fin...', 'categoryId', Array)
#3 /www/htdocs/w0104af9/wundr-shop.de/ebay-sdk-php/DTS/eBaySDK/Types/BaseType.php(85): DTS\eBaySDK\Types\BaseType->set('DTS\\eBaySDK\\Fin...', 'categoryId', Array)
#4 /www/htdocs/w0104af9/wundr-shop.de/sites/static/product/index.php(100): DTS\eBaySDK\Types\BaseType->__set('categoryId', Array)
#5 /www/htdocs/w0104af9/wundr-shop.de/lib/Site.php(29): require('/www/htdocs/w01...')
#6 [internal function]: lib\Site::lib\{closure}('ferienhaus-mit-...')
#7 /www/htdocs/w0104af9/wundr-shop.de/vendor/illuminate/routing/Route.php(157): call_user_func_array(Object(Closure), Array)
#8 /www/htdocs/w0104af9/wundr-shop.de/vendor/illuminate/routing/Route.php(129): Illuminate\Routing\Route->runCallable(Object(lib\Request))
#9 /www/htdocs/w0104af9/wundr-shop.de/vendor/illuminate/routing/Router.php(701): Illuminate\Routing\Route->run(Object(lib\Request))
#10 [internal function]: Illuminate\Routing\Router->Illuminate\Routing\{closure}(Object(lib\Request))
#11 /www/htdocs/w0104af9/wundr-shop.de/vendor/illuminate/pipeline/Pipeline.php(141): call_user_func(Object(Closure), Object(lib\Request))
#12 [internal function]: Illuminate\Pipeline\Pipeline->Illuminate\Pipeline\{closure}(Object(lib\Request))
#13 /www/htdocs/w0104af9/wundr-shop.de/vendor/illuminate/pipeline/Pipeline.php(101): call_user_func(Object(Closure), Object(lib\Request))
#14 /www/htdocs/w0104af9/wundr-shop.de/vendor/illuminate/routing/Router.php(703): Illuminate\Pipeline\Pipeline->then(Object(Closure))
#15 /www/htdocs/w0104af9/wundr-shop.de/vendor/illuminate/routing/Router.php(670): Illuminate\Routing\Router->runRouteWithinStack(Object(Illuminate\Routing\Route), Object(lib\Request))
#16 /www/htdocs/w0104af9/wundr-shop.de/vendor/illuminate/routing/Router.php(628): Illuminate\Routing\Router->dispatchToRoute(Object(lib\Request))
#17 /www/htdocs/w0104af9/wundr-shop.de/lib/App.php(90): Illuminate\Routing\Router->dispatch(Object(lib\Request))
#18 /www/htdocs/w0104af9/wundr-shop.de/public/index.php(48): lib\App::start()
#19 {main}