message: fix: add safeguard for undefined
  closes
diff: @@ -189,7 +189,7 @@ export class SpecManager {
  // check if parent definition name is in the enum of possible values
  if (definition.discriminator) {
  let prop = definition.properties[definition.discriminator];
  - if (prop.enum && prop.enum.indexOf(JsonPointer.baseName(defPointer)) > -1) {
  + if (prop && prop.enum && prop.enum.indexOf(JsonPointer.baseName(defPointer)) > -1) {
  res.push({
  name: JsonPointer.baseName(defPointer),
  $ref: defPointer
  