message: Guard against nullable typename fields
  This should never happen but I figured given the
  changes in write we should at least have a case
  for this.
diff: @@ -21,11 +21,13 @@ interface Context {
  const isFragmentMatching = (
  node: InlineFragmentNode | FragmentDefinitionNode,
  - typename: string,
  + typename: void | string,
  entityKey: string,
  ctx: Context
  ) => {
  - if (typename === getTypeCondition(node)) {
  + if (!typename) {
  + return false;
  + } else if (typename === getTypeCondition(node)) {
  return true;
  }
  @@ -40,7 +42,7 @@ const isFragmentMatching = (
  };
  export const forEachFieldNode = (
  - typename: string,
  + typename: void | string,
  entityKey: string,
  select: SelectionSet,
  ctx: Context,
  