(fix) デフォルト表示時のヘッダにあるチャンネルボタンが反応しない現象の修正 (#12648)

* dividerの仕変に追従

* fix type

packages/frontend/src/pages/timeline.vue

@@ -125,14 +125,14 @@ async function chooseChannel(ev: MouseEvent): Promise<void> {
 	const channels = await os.api('channels/my-favorites', {
 		limit: 100,
 	});
-	const items = [
+	const items: MenuItem[] = [
 		...channels.map(channel => ({
 			type: 'link' as const,
 			text: channel.name,
 			indicate: channel.hasUnreadNote,
 			to: `/channels/${channel.id}`,
 		})),
-		(channels.length === 0 ? undefined : null),
+		(channels.length === 0 ? undefined : { type: 'divider' }),
 		{
 			type: 'link' as const,
 			icon: 'ti ti-plus',