rem: if( !this.pageData[aPageTag] ) 
add: if( !(aPageTag in this.pageData) ) 
context:         setItemData:          function ( aPageTag, aItemID, aDataObject )            {              if( !this.pageData[aPageTag] )                this.pageData[aPageTag] = [];              this.pageData[aPageTag][aItemID] = aDataObject;            },
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/66c41c404dac77d053bf9bb78c8621d6e34494dc/nsWidgetStateManager.js/buggy/xpfe/global/resources/content/nsWidgetStateManager.js