ModalPopup JScript runtime error on properties Drag="true"

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ASP.NET

Ajax

Hi
I am Using .Net framework 4.0 and Ajax 4.1.50401.0 I have ModalPopup inside update panel with properties Drag="true". When a user clicks on blank area of panel, I am getting java script runtime error like:

Microsoft JScript runtime error:  Unknown runtime error

Please refer the below statements which is auto generated, for more clarification.

_onDragStart: function(ev) {

        window._event = ev;

        document.selection.empty();

 

        var dt = ev.dataTransfer;

        if (!dt && ev.rawEvent) dt = ev.rawEvent.dataTransfer;

 

        var dataType = this._activeDragSource.get_dragDataType().toLowerCase();

        var data = this._activeDragSource.getDragData(this._activeContext);

 

        if (data) {

            if (dataType != "text" && dataType != "url") {

                dataType = "text";

 

                if (data.innerHTML != null) {

                    data = data.innerHTML;

                }

            }

 

            dt.effectAllowed = "move";

            dt.setData(dataType, data.toString());

        }

    },