title: Json model not updating
body: <p>I have model:</p>
  
  <pre><code>$scope.newTask = function() {
          return {
              ProjectID: null,
              ProjectName: null,
              Date: getDate(),
              TaskDescription: null,
              TimeWorked: '1',
              Note: null,
              isSaved: false
          };
      };
  </code></pre>
  
  <p>I updated model:</p>
  
  <pre><code>$scope.newTask = function() {
      return {
          ProjectId: null,
          ProjectName: null,
          Date: getDate(),
          Task: null,
          TimeWorked: '1',
          Note: null,
          isSaved: false
      };
  };
  </code></pre>
  
  <p>After update, my browser returns me model with old an new fields. How I can solve this? I don't need old fields in object...</p>