fix robust error bug: recalculate best_error
fix robust error bug: recalculate best_error

ppwwyyxx/OpenPano,ppwwyyxx/OpenPano,ppwwyyxx/panorama,ppwwyyxx/OpenPano,ChenXiaoTemp/panorama,ppwwyyxx/panorama,ChenXiaoTemp/panorama,ppwwyyxx/panorama,ChenXiaoTemp/panorama