rem: this.popup.feature = null; this.popup.destroy() 
add: if (this.popup) { this.popup.feature = null; this.popup.destroy(); this.popup = null; } 
context:     destroyPopup: function() {        this.popup.feature = null;        this.popup.destroy()     },
meta: 1027	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/1027/b9a04a0e9b37c58dc74bdbaac24de7ef3561c3de/Feature.js/clean/lib/OpenLayers/Feature.js