message: this fixes a bug where if a vendor does not exit on the GVL and narrowVendorsTo is called with that vendor id it throws an error
diff: @@ -588,7 +588,7 @@ export class GVL extends Cloneable<GVL> implements VendorList {
  const vendor: Vendor = this.vendors_[''+vendorId];
  - if (vendor.deletedDate === undefined) {
  + if (vendor && vendor.deletedDate === undefined) {
  vendor.purposes.forEach((purposeId: number): void => {
  