message: Add guard code around updateQuery
diff: @@ -184,10 +184,14 @@ export class Store {
  updateQuery(
  dataQuery: DocumentNode,
  - updater: (data: Data | null) => Data
  + updater: (data: Data | null) => null | Data
  ): void {
  - const { data } = startQuery(this, { query: dataQuery });
  - startWrite(this, { query: dataQuery }, updater(data));
  + const { data, completeness } = startQuery(this, { query: dataQuery });
  + const input = completeness === 'EMPTY' ? null : data;
  + const output = updater(input);
  + if (output !== null) {
  + startWrite(this, { query: dataQuery }, output);
  + }
  }
  writeFragment(dataFragment: DocumentNode, data: Data): void {
  