fix(oas31): render responses with empty content field (#9664)

Refs #9199

src/core/plugins/json-schema-2020-12-samples/fn/main.js

@@ -21,6 +21,9 @@ export const sampleFromSchemaGeneric = (
   exampleOverride = undefined,
   respectXML = false
 ) => {
+  // there is nothing to generate schema from
+  if (schema == null && exampleOverride === undefined) return undefined
+
   if (typeof schema?.toJS === "function") schema = schema.toJS()
   schema = typeCast(schema)
 

src/core/plugins/oas31/after-load.js

@@ -27,6 +27,10 @@ function afterLoad({ fn, getSystem }) {
         createXMLExample: fn.jsonSchema202012.createXMLExample,
         memoizedSampleFromSchema: fn.jsonSchema202012.memoizedSampleFromSchema,
         memoizedCreateXMLExample: fn.jsonSchema202012.memoizedCreateXMLExample,
+        getJsonSampleSchema: fn.jsonSchema202012.getJsonSampleSchema,
+        getYamlSampleSchema: fn.jsonSchema202012.getYamlSampleSchema,
+        getXmlSampleSchema: fn.jsonSchema202012.getXmlSampleSchema,
+        getSampleSchema: fn.jsonSchema202012.getSampleSchema,
       },
       getSystem()
     )