Fix a bug regarding the new grouping

src/lib/components/calendar/List/List.svelte

@@ -1,3 +1,11 @@
+<script lang="ts" context="module">
+	function groupEvents(events: Calendar[]) {
+		const grouped = groupBy(events, ({ beginning }) => stringify(beginning));
+		const values = Object.values(grouped);
+		return values.map((x) => x!);
+	}
+</script>
+
 <script lang="ts">
 	import Store from '$lib/components/utils/Store.svelte';
 	import type { Calendar } from '$lib/dlool/calendar/list';
@@ -7,7 +15,8 @@
 	import CalEventListBox from './CalEventListBox.svelte';
 
 	export let events: Calendar[];
-	$: grouped = Object.values(groupBy(events, ({ beginning }) => stringify(beginning)));
+
+	$: grouped = groupEvents(events);
 </script>
 
 {#each grouped as day, index}

src/lib/utils/objects/group.ts

@@ -9,7 +9,10 @@ type Key = string | number | symbol;
  * @param {(item: T) => K} keySelector A function that extracts the key for grouping from each element.
  * @returns {Record<K, T[]>} An object where keys are derived from elements and values are arrays of elements with the same key.
  */
-export function groupBy<T, K extends Key>(array: T[], keySelector: (item: T) => K): Record<K, T[]> {
+export function groupBy<T, K extends Key>(
+	array: T[],
+	keySelector: (item: T) => K
+): Partial<Record<K, T[]>> {
 	return array.reduce(
 		(result, item) => {
 			const key = keySelector(item);

src/routes/homework/+page.svelte

@@ -92,8 +92,8 @@
 					})}
 					<div class="h-full w-full">
 						<AssignmentGrid
-							assignments={grouped.upcoming}
-							overdueAssignments={grouped.overdue}
+							assignments={grouped.upcoming ?? []}
+							overdueAssignments={grouped.overdue ?? []}
 							school={data.query.school}
 							on:delete={invalidateAll}
 							on:update={invalidateAll}