The function sortByZOrder() throws the exception if a frame consists any points

[bsekachev]

Scenario:

• In a task with the enabled z-order flag try to change z-order for a points shape.

Uncaught TypeError: Cannot read property 'nodeValue' of undefined
    at content.find.toArray.sort (shapeCollection.js:1568)
    at Array.sort (:7000/native)
    at Function.sortByZOrder (shapeCollection.js:1567)
    at PointsView.onShapeUpdate (shapes.js:2485)
    at PointsModel.notify (listener.js:48)
    at PointsModel.notify (shapes.js:203)
    at PointsModel.set active [as active] (shapes.js:519)
    at ShapeCollectionModel.resetActive (shapeCollection.js:485)
    at ShapeCollectionController.resetActive (shapeCollection.js:1078)
    at HTMLDivElement.ShapeCollectionView.$.on (shapeCollection.js:1211)