fix: let a calendar event's repeat, description and location be cleared again (#30204)

src/lib/apis/calendar/index.ts

@@ -53,7 +53,7 @@ export type CalendarEventForm = {
 	start_at: number;
 	end_at?: number;
 	all_day?: boolean;
-	rrule?: string;
+	rrule?: string | null;
 	color?: string;
 	location?: string | null;
 	data?: Record<string, any>;

src/lib/components/calendar/CalendarEventModal.svelte

@@ -140,12 +140,12 @@
 				const result = await updateCalendarEvent(localStorage.token, event.id, {
 					calendar_id: calendarId,
 					title: title.trim(),
-					description: description.trim() || undefined,
+					description: description.trim() || null,
 					start_at: startNs,
 					end_at: endNs,
 					all_day: allDay,
-					rrule: getRepeatRrule(),
-					location: location.trim() || undefined,
+					rrule: getRepeatRrule() ?? null,
+					location: location.trim() || null,
 					meta: { alert_minutes: alertMinutes }
 				});
 				if (result) {