无法从地图中删除标记（无法读取属性'unselectAll'）

Question

我正在尝试从地图中删除标记，但我无法使用。我可以选择它，移动它但是当我尝试删除它时它什么也没做。

当我点击删除选项时，会弹出以下js错误：

Uncaught TypeError: Cannot read property 'unselectAll' of undefined openlayers_behavior_geofield.js?n5kot1:39
controls.push.OpenLayers.Control.ModifyFeature.handleKeypress openlayers_behavior_geofield.js?n5kot1:39
OpenLayers.Handler.OpenLayers.Class.callback OpenLayers.js?n5kot1:205
OpenLayers.Handler.Keyboard.OpenLayers.Class.handleKeyEvent OpenLayers.js?n5kot1:647
(anonymous function) OpenLayers.js?n5kot1:63

任何人都知道为什么会发生这种情况？

我正在使用Openlayers 7.x-2.0-beta9和Geofield 7.x-2.1

谢谢！

失败的Geofield文件（openlayers_behavior_geofield.js）：

if (options.allow_edit && options.allow_edit !== 0) {
    // add an Edit feature
    controls.push(new OpenLayers.Control.ModifyFeature(layer, {
        deleteCodes: [46, 68, 100],
        handleKeypress: function(evt) {
            if (this.feature && OpenLayers.Util.indexOf(this.deleteCodes, evt.keyCode) > -1) {
                // We must unselect the feature before we delete it
                var feature_to_delete = this.feature;
                this.selectControl.unselectAll();
                this.layer.removeFeatures([feature_to_delete]);
            }
        }
    }));
}