fix(next): re-throw unhandled errors in DocumentView to prevent blank edit views

[litlmike]

Description

When renderDocument throws an error that is neither NEXT_REDIRECT nor not-found, the catch block in DocumentView (packages/next/src/views/Document/index.tsx) logs the error but returns undefined. React renders undefined as empty content inside the Suspense boundary, producing a completely blank edit view with no visible error.

// BEFORE — silent fallthrough returns undefined
export async function DocumentView(props: AdminViewServerProps) {
  try {
    const { Document: RenderedDocument } = await renderDocument(props)
    return RenderedDocument
  } catch (error) {
    if (error?.message === 'NEXT_REDIRECT') { throw error }
    logError({ err: error, payload: props.initPageResult.req.payload })
    if (error.message === 'not-found') { notFound() }
    // ⚠️ Falls through here → returns undefined → blank page
  }
}

The Fix

Add throw error at the end of the catch block so unhandled errors propagate to Next.js error boundaries instead of rendering blank.

This is a one-line fix. The comment block explains why it exists for future maintainers.

Impact

• No behavior change for Node.js deployments where errors in this path are already not-found or NEXT_REDIRECT
• Fixes blank edit views on edge runtimes (Cloudflare Workers/Pages, Vercel Edge) where auth-context failures, streaming issues, or missing Node.js APIs produce errors that fall through the unhandled path
• Error boundaries now render visible errors instead of blank pages, making debugging possible

Root Cause Analysis

On Cloudflare Workers, renderDocument does heavy async work — two Promise.all calls fetching permissions, lock state, versions, and form state. Any of these can fail on edge runtimes due to:

• Auth context/cookie access differences (confirmed in Server Actions lose authentication in Cloudflare Workers environment #14656)
• Transaction isolation issues with D1
• Missing Node.js APIs in the Workers runtime
• RSC streaming constraints

These errors are neither not-found nor NEXT_REDIRECT, so they hit the unhandled path and the function silently returns undefined.

Testing

Added DocumentView.spec.ts with vitest cases verifying:

1. Unhandled errors are re-thrown (not swallowed)
2. NEXT_REDIRECT errors propagate correctly
3. The function never returns undefined

Related Issues

Fixes #15712 — Edit views render blank on Cloudflare Pages (empty RSC Suspense boundaries)
Relates to #14656 — Server Actions lose authentication in Cloudflare Workers environment
Relates to opennextjs/opennextjs-cloudflare#544 — PayloadCMS not working with opennextjs