message: fixed to support '' id
diff: @@ -899,7 +899,7 @@ export class columnImpl<colType, rowType> implements EntityColumn<colType, rowTy
  get inputValue(): string {
  let lu = this.rowBase.lookups.get(this.defs.key);
  if (lu)
  - return lu.id ? lu.id.toString() : null;
  + return lu.id!=undefined ? lu.id.toString() : null;
  return this.defs.valueConverter.toInput(this.value, this.settings.inputType);
  }
  set inputValue(val: string) {
  