Custom fields configuration might be null and leads to a fatal error

[fairlane]

Shopware version(s) used: 5.6.7
Extension version(s) affected: 2.4.8

Description
Detail::getConfiguratorOptions might return null and leads to a fatal error here https://github.com/Nosto/nosto-shopware/blob/master/Components/Helper/CustomFields.php#L83

How to reproduce
Create a product that doesn't have configurator options.

Possible Solution
Add a null guard for Detail::getConfiguratorOptions