message: added init "null" value for matrixdropdown rowValues
diff: @@ -177,6 +177,11 @@ export class MatrixDropdownRowModelBase implements ISurveyData, ILocalizableOwne
  constructor(data: IMatrixDropdownData, value: any) {
  this.data = data;
  this.value = value;
  + for (var i = 0; i < this.data.columns.length; i++) {
  + if(this.rowValues[this.data.columns[i].name] === undefined) {
  + this.rowValues[this.data.columns[i].name] = null;
  + }
  + }
  this.idValue = MatrixDropdownRowModelBase.getId();
  this.buildCells();
  }
  @@ -218,7 +223,9 @@ export class MatrixDropdownRowModelBase implements ISurveyData, ILocalizableOwne
  public get isEmpty() {
  var val = this.value;
  if (Base.isValueEmpty(val)) return true;
  - for (var key in val) return false;
  + for (var key in val) {
  + if (val[key] !== undefined && val[key] !== null) return false;
  + }
  return true;
  }
  public getLocale(): string { return this.data ? this.data.getLocale() : "";}
  