Nested model attribute is null in response

@Boegie19 I get this error when I try to invoke the api type?[slug]=slug-string&populate=*

{"statusCode":400,"error":"Bad Request","message":"Your filters contain a field 'populate' that doesn't appear on your model definition nor its relations"}

I also tried installing a plugin called strapi-plugin-populate-deep. That did not help either. I am trying hard not to write controllers for this and just use the out of the box features of strapi.