fix(desktop): filter undefined entries in AttachmentList to prevent refText crash on session switch (#49624)

* fix(desktop): filter undefined entries in AttachmentList to prevent refText crash on session switch

When switching sessions, the attachments array can contain stale/undefined
entries from the previous session's state. Accessing attachment.refText on
an undefined entry throws TypeError, breaking session switching entirely.

Fix: add .filter(Boolean) before .map() to skip undefined/null entries.

Fixes #49614

* fix(desktop): update I18nConfigClient usage in attachment test

The i18n config API changed from getLocale/saveLocale to
getConfig/saveConfig. Update the test fixture to match.

apps/desktop/src/app/chat/composer/attachments.test.tsx

@@ -0,0 +1,69 @@
+import { cleanup, render, screen } from '@testing-library/react'
+import { afterEach, describe, expect, it } from 'vitest'
+
+import { I18nProvider } from '@/i18n/context'
+
+import { AttachmentList } from './attachments'
+import type { ComposerAttachment } from '@/store/composer'
+
+function makeAttachment(id: string, label = 'test.pdf'): ComposerAttachment {
+  return { id, kind: 'file', label }
+}
+
+function renderWithI18n(ui: React.ReactNode) {
+  return render(
+    <I18nProvider configClient={{ getConfig: async () => ({}), saveConfig: async () => ({ ok: true }) }}>
+      {ui}
+    </I18nProvider>
+  )
+}
+
+describe('AttachmentList', () => {
+  afterEach(() => {
+    cleanup()
+  })
+
+  it('renders valid attachments', () => {
+    const attachments = [makeAttachment('a', 'doc.pdf'), makeAttachment('b', 'img.png')]
+    renderWithI18n(<AttachmentList attachments={attachments} />)
+    expect(screen.getByText('doc.pdf')).toBeDefined()
+    expect(screen.getByText('img.png')).toBeDefined()
+  })
+
+  it('renders empty list without error', () => {
+    renderWithI18n(<AttachmentList attachments={[]} />)
+    const container = screen.getByTestId?.('composer-attachments') ?? document.querySelector('[data-slot="composer-attachments"]')
+    expect(container).toBeDefined()
+  })
+
+  it('does not crash when attachments array contains undefined entries', () => {
+    // Repro: session switch can leave stale/undefined entries in the
+    // attachments array, causing a TypeError at attachment.refText.
+    const attachments = [
+      makeAttachment('a', 'good.pdf'),
+      undefined as unknown as ComposerAttachment,
+      makeAttachment('b', 'also-good.png')
+    ]
+
+    expect(() => {
+      renderWithI18n(<AttachmentList attachments={attachments} />)
+    }).not.toThrow()
+
+    // Only valid attachments should render
+    expect(screen.getByText('good.pdf')).toBeDefined()
+    expect(screen.getByText('also-good.png')).toBeDefined()
+  })
+
+  it('does not crash when attachments array contains null entries', () => {
+    const attachments = [
+      null as unknown as ComposerAttachment,
+      makeAttachment('a', 'valid.txt')
+    ]
+
+    expect(() => {
+      renderWithI18n(<AttachmentList attachments={attachments} />)
+    }).not.toThrow()
+
+    expect(screen.getByText('valid.txt')).toBeDefined()
+  })
+})

apps/desktop/src/app/chat/composer/attachments.tsx

@@ -20,7 +20,7 @@ export function AttachmentList({
 }) {
   return (
     <div className="flex max-w-full flex-wrap gap-1.5 px-1 pt-1" data-slot="composer-attachments">
-      {attachments.map(attachment => (
+      {attachments.filter(Boolean).map(attachment => (
         <AttachmentPill attachment={attachment} key={attachment.id} onRemove={onRemove} />
       ))}
     </div>