TypeError: this.toolbars is undefined ? CQ 5.4 ?Panel & MultiField

Hi,

We have recently upgraded from CQ 5.3 to 5.4 Author. All of our custom multifield xtype widgets are stopped working, when we drilled down a JS error has been noticed constantly after click and init.

TypeError: this.toolbars is undefined

http://localhost:4502/libs/cq/ui/widgets.js

Line 31397

Which is occurring at panel.js

onLayout : function(shallow, force){

CQ.Ext.Panel.superclass.onLayout.apply(this, arguments);

                if(this.hasLayout && this.toolbars.length > 0){

            CQ.Ext.each(this.toolbars, function(tb){

                tb.doLayout(undefined, force);

            });

            this.syncHeight();

        }

    },

Any pointers to this would be appreciated.