Dojo : Cannot read property 'h' of undefined on AccordionContainer.js?-Collection of common programming errors

I am getting an error like this when I created Two accordion containers dynamically under an accordion container.

The error will not happens when I created any of these single accordion container instead of create both together.

Error :

Cannot read property ‘h’ of undefined on AccordionContainer.js

I have temporarily fix the problem by adding these lines to tool kit file, dojo-toolkit\dijit\layout\AccordionContainer.js

Line 91: + if(this._contentBox) 
Line 92:    this._verticalSpace=_34.h-_35-_2f.h-_30.h-_32.h-_33.h-_2d._buttonWidget.getTitleHeight(); 
Line 93: + if(this._contentBox) 
Line 94:    this._containerContentBox={h:this._verticalSpace,w:this._contentBox.w-_2f.w-_30.w-_32.w- _33.w}; 

Accordion Widget creation code structure is

define("test/project", [ 
        "dojo/_base/declare", 
        "dijit/_Widget", 
        "dijit/layout/AccordionContainer"], 
    function(declare, _Widget, AccordionContainer) { 
        return declare([_Widget],{ 
                         postCreate: function() { 
                                var new_acc = new AccordionContainer({ 
                                        id: "new_acc", 
                                        title: "Approval ("+this.count+")" 
                                }); 

                               this.parentId.addChild(new_acc); 
                        } 
        });     
}); 

Any idea to solve this issue?

Thanks in advance…