Livechat widget: thread rendering throws when a parent message can't be fetched (unguarded destructures)

Description:

In the Livechat widget, thread-reply messages resolve their quoted-parent context via normalizeThreadMessage in packages/livechat/src/lib/threads.ts. When the parent message can't be fetched, two unguarded operations make rendering throw instead of degrading gracefully:

Bug A — findParentMessage catch block re-throws (lines 43-45):

} catch (error: any) {
	const {
		data: { error: reason },   // TypeError when `error.data` is undefined
	} = error;

Livechat.message() rejects with a plain network/timeout error (no .data payload) on connection failures. Destructuring data: { error } from such an error throws a new TypeError inside the catch block, swallowing the original error and skipping the intended user-facing alert.

Bug B — normalizeThreadMessage destructures a possibly-undefined parent (line 62):

parentMessage = await findParentMessage(message.tmid);   // undefined when the fetch failed
const { msg, attachments = [] } = parentMessage;          // TypeError: Cannot destructure property 'msg' of 'undefined'

Even when Bug A doesn't fire (an HTTP error that does carry .data), findParentMessage returns undefined, and line 62 crashes destructuring it.

Steps to reproduce:

1. Enable Livechat and open the widget as a visitor.
2. Have an agent reply to a message in a thread (so the visitor's history contains a message with tmid whose parent is not in the current batch).
3. Trigger a failed parent fetch — e.g. block/offline the Livechat.message request, or delete the parent message server-side, then reload the widget history (loadMessages).
4. The message list fails to render instead of showing the reply without its quoted context.

Expected behavior:

When a thread's parent message can't be loaded, the widget should still render the reply (without the quoted-parent preview) and/or show the graceful alert — never throw.

Actual behavior:

An unhandled TypeError is thrown from threads.ts (either the catch-block destructure or the parentMessage destructure), breaking message rendering.

Server Setup Information:

• Version of Rocket.Chat Server: develop (client-side bug in @rocket.chat/livechat; server-version independent)

Client Setup Information:

• Rocket.Chat Livechat widget (@rocket.chat/livechat), any browser.

Additional context

Distinct from #42002 (which fixes the normalizeMessages async-filter no-op). This is a separate error-handling defect in the same file; the open PR #42089 does not touch these lines.

Proposed fix (minimal guards):

// Bug A — findParentMessage catch
const reason = error?.data?.error ?? error?.message ?? 'Could not load message';

// Bug B — normalizeThreadMessage
if (!parentMessage) {
	return message;   // render the reply without quoted context
}

I'd like to work on this and will open a PR.

Start in packages/livechat/src/lib/threads.ts, reading findParentMessage and normalizeThreadMessage and following their use during loadMessages. Reproduce a failed Livechat.message request, then verify the reply still renders without quoted-parent context and that the intended graceful alert is preserved rather than a TypeError being thrown.