can't check for NoneDataType, it may be wrapped.

Author: hauner

openapi-processor-core/src/main/kotlin/io/openapiprocessor/core/model/EmptyResponse.kt

@@ -15,4 +15,7 @@ class EmptyResponse(
     contentType: String = "?",
     responseType: DataType = NoneDataType(),
     description: String? = null
-): Response(contentType, responseType, description)
+): Response(contentType, responseType, description) {
+    override val empty
+        get() = true
+}

openapi-processor-core/src/main/kotlin/io/openapiprocessor/core/model/Response.kt

@@ -6,7 +6,6 @@
 package io.openapiprocessor.core.model
 
 import io.openapiprocessor.core.model.datatypes.DataType
-import io.openapiprocessor.core.model.datatypes.NoneDataType
 
 /**
  * Endpoint response properties.
@@ -19,6 +18,6 @@ open class Response(
     val imports
         get() = responseType.getImports()
 
-    val empty
-        get() = responseType is NoneDataType
+    open val empty
+        get() = false
 }