fix: add null checks to chat iterators in ArchivedChats and FolderPlaceholder (#19898)

src/lib/components/chat/Placeholder/FolderPlaceholder.svelte

@@ -1,6 +1,8 @@
-<script>
+<script lang="ts">
 	import { getContext, onMount } from 'svelte';
-	const i18n = getContext('i18n');
+	import type { Writable } from 'svelte/store';
+
+	const i18n: Writable<any> = getContext('i18n');
 
 	import { fade } from 'svelte/transition';
 
@@ -9,13 +11,13 @@
 	import Spinner from '$lib/components/common/Spinner.svelte';
 	import { getChatListByFolderId } from '$lib/apis/chats';
 
-	export let folder = null;
+	export let folder: any = null;
 
 	let selectedTab = 'chats';
 
 	let page = 1;
 
-	let chats = null;
+	let chats: any[] | null = null;
 	let chatListLoading = false;
 	let allChatsLoaded = false;
 
@@ -24,7 +26,7 @@
 
 		page += 1;
 
-		let newChatList = [];
+		let newChatList: any[] = [];
 
 		newChatList = await getChatListByFolderId(localStorage.token, folder.id, page).catch(
 			(error) => {
@@ -35,7 +37,7 @@
 
 		// once the bottom of the list has been reached (no results) there is no need to continue querying
 		allChatsLoaded = newChatList.length === 0;
-		chats = [...chats, ...newChatList];
+		chats = [...(chats || []), ...(newChatList || [])];
 
 		chatListLoading = false;
 	};