Wrap pageInfo in non-null.
Wrap pageInfo in non-null.

To fit with spec.

BenjaminMalley/graphql-java,dminkovsky/graphql-java,graphql-java/graphql-java,dminkovsky/graphql-java,fderose/graphql-java,blevandowski-lv/graphql-java,blevandowski-lv/graphql-java,fderose/graphql-java,graphql-java/graphql-java