OpenLayers 2.13.1 compatibility

[demiurg]

The new version of OpenLayers has been released, and it seems that it has some backwards incompatibilities with 2.12:

Uncaught TypeError: Cannot set property 'onUnselect' of undefined olwidget.js:1520 olwidget.DeleteVertex.OpenLayers.Class.initialize olwidget.js:1520 olwidget.EditableLayer.OpenLayers.Class.buildControls olwidget.js:701 olwidget.EditableLayer.OpenLayers.Class.setMap olwidget.js:639 OpenLayers.Map.OpenLayers.Class.addLayer OpenLayers.js:173 OpenLayers.Map.OpenLayers.Class.addLayers OpenLayers.js:173 olwidget.Map.OpenLayers.Class.initMap olwidget.js:299 olwidget.Map.OpenLayers.Class.initialize olwidget.js:207 (anonymous function)