Not sure which version you are on, but the contentConnector is a Magnolia 5 configuration that is usable in Magnolia 6 but deprecated.
I do not see any “class” or “appClass” defined at the root of the app, which could be the reason for the NPE https://docs.magnolia-cms.com/product-docs/6.2/apps/app-configuration/app-descriptor/
I hope this helps.
Best regards,
Roman