message: fix: avoid endless recursion in schema-walker in some cases
  fixes
diff: @@ -53,6 +53,15 @@ class SchemaWalker {
  if (obj == undefined || typeof(obj) !== 'object') {
  return;
  }
  +
  + if (obj['x-redoc-visited']) {
  + const res = visitor(obj, pointer);
  + obj['x-redoc-visited'] = false;
  + // circular, return only title and description
  + return { title: res.title, description: res.description }
  + }
  +
  + obj['x-redoc-visited'] = true;
  if (obj.properties) {
  let ptr = JsonPointer.join(pointer, ['properties']);
  SchemaWalker.walkEach(obj.properties, ptr, visitor);
  @@ -83,7 +92,9 @@ class SchemaWalker {
  }
  }
  - return visitor(obj, pointer);
  + const res = visitor(obj, pointer);
  + obj['x-redoc-visited'] = false;
  + return res;
  }
  private static walkEach(obj:Object, pointer:string, visitor:Function) {
  