rem: if( icalcomponent_get_first_property(comp,ICAL_DTEND_PROPERTY)){
add: if( !icalcomponent_get_first_property(comp,ICAL_DTEND_PROPERTY)){
context: char* icalrestriction_no_dtend(icalrestriction_property_record *rec,			       icalcomponent* comp, 			       icalproperty* prop){    if( icalcomponent_get_first_property(comp,ICAL_DTEND_PROPERTY)){	return "Failed iTIP restrictions for DTEND property. The component must not have both DURATION and DTEND";    }    return 0;    }