ClassCastException when walking over input types that have GraphQLTypeReferences #99

java.lang.ClassCastException: class graphql.schema.GraphQLTypeReference cannot be cast to class graphql.schema.GraphQLUnmodifiedType (graphql.schema.GraphQLTypeReference and graphql.schema.GraphQLUnmodifiedType are in unnamed module of loader 'app')
  at graphql.schema.GraphQLTypeUtil.unwrapAll(GraphQLTypeUtil.java:194)
  at graphql.validation.util.DirectivesAndTypeWalker.walkInputType(DirectivesAndTypeWalker.java:23)
  at graphql.validation.util.DirectivesAndTypeWalker.isSuitable(DirectivesAndTypeWalker.java:19)

enum SlotType {
    AVAILABLE, UNAVAILABLE
}

type Employee {
  schedule(type: SlotType!): [Slot!]!
}

Unwraps all layers of the type or just returns the type again if it's not a wrapped type NOTE: This method does not support GraphQLTypeReference as input and will lead to a ClassCastException

type = {GraphQLNonNull@17904} "SlotType!"
 originalWrappedType = {GraphQLTypeReference@17955} "GraphQLTypeReference{name='SlotType'}"
  name = "SlotType"
 replacedWrappedType = null