message: Fix null customOptions error
diff: @@ -490,12 +490,12 @@ export module Utils {
  }
  // Merge two objects
  - export function merge<T>(source: T, target: T): T {
  + export function merge<T>(source: T, target: T, acceptNull = false): T {
  let result = <T>{};
  for (let prop in source) {
  - if (prop in target) {
  + if (prop in target && (target[prop] !== null || acceptNull)) {
  if (Utils.Obj.isObject(source[prop]) && Utils.Obj.isObject(target[prop])) {
  - result[prop] = Utils.Obj.merge(source[prop], target[prop]);
  + result[prop] = Utils.Obj.merge(source[prop], target[prop], acceptNull);
  } else {
  result[prop] = target[prop];
  }
  @@ -505,7 +505,7 @@ export module Utils {
  }
  for (let prop in target) {
  - if (!(prop in source)) {
  + if (!(prop in source) && (target[prop] !== null || acceptNull)) {
  result[prop] = target[prop];
  }
  }
  