add: if (! vNewItem) { return; }  
context: qx.Proto._onkeyup = function(e){  if (this._fastUpdate)  {    var vOldItem = this._oldItem;    var vNewItem = this.getManager().getSelectedItem();    vNewItem.getIconObject().addState(qx.manager.selection.SelectionManager.STATE_SELECTED);    delete this._fastUpdate;    delete this._oldItem;  };};
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