rem: this.mCalMgr.deleteCalendarPref(this.mDefaultCalendar, this.mDefaultPref); 
add: if (this.mDefaultCalendar) { this.mCalMgr.deleteCalendarPref(this.mDefaultCalendar, this.mDefaultPref); } 
context:     setDefaultCalendar: function (cal, usePref) {        if (this.mDefaultCalendar && this.mDefaultCalendar.uri.equals(cal.uri))            return;        if (usePref && this.mPrefPrefix) {            this.mCalMgr.deleteCalendarPref(this.mDefaultCalendar,                                            this.mDefaultPref);            this.mCalMgr.setCalendarPref(cal, this.mDefaultPref,                                         "true");        }        this.mDefaultCalendar = cal;        this.notifyObservers("onDefaultCalendarChanged", [cal]);    },
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/f4cdcf5693e75a843e733384f55fa3493419dacf/calCompositeCalendar.js/clean/calendar/providers/composite/calCompositeCalendar.js