fix(Page): prevent crash when document fails to load

[cyphercodes]

Description

When the Document component fails to load a PDF (e.g., 403 or 404 error), it sets pdf to false. The Page component was throwing an invariant error when pdf was false, causing the entire UI to crash even when error handlers were provided.

The Problem

Users reported that when a document fails to load with an error, the whole UI crashes even though they have error handlers in place:

<Document
  file={url}
  onLoadError={() => onFileLoadError?.()}
  error={<div>ERROR</div>}
>
  {numPages && (
    <Page pageNumber={currentPage} ... />
  )}
</Document>

The Fix

Changed the invariant check from:

invariant(pdf, '...')

to:

invariant(pdf !== null && pdf !== undefined, '...')

This allows pdf to be false (indicating a load error) and lets the renderContent() function handle it gracefully by showing the error message instead of throwing an error.

Changes

• Modified the invariant check in Page.tsx to allow pdf === false
• The existing error handling in renderContent() already handles pdf === false correctly

Fixes #2051