Check stack property for page export exceptions (#32289)

Co-authored-by: JJ Kasper <jj@jjsweb.site>

packages/next/export/worker.ts

@@ -503,7 +503,7 @@ export default async function exportPage({
     } catch (error) {
       console.error(
         `\nError occurred prerendering page "${path}". Read more: https://nextjs.org/docs/messages/prerender-error\n` +
-          (isError(error) ? error.stack : error)
+          (isError(error) && error.stack ? error.stack : error)
       )
       results.error = true
     }

test/integration/handles-export-errors/pages/custom-error.js

@@ -0,0 +1,13 @@
+class CustomError {
+  constructor(message, data) {
+    this.message = message
+    this.data = data
+  }
+  toString() {
+    return this.message
+  }
+}
+
+export default () => {
+  throw new CustomError('custom error message', {})
+}

test/integration/handles-export-errors/test/index.test.js

@@ -21,5 +21,7 @@ describe('Handles Errors During Export', () => {
     expect(stderr).toContain('/page-13')
     expect(stderr).toContain('/blog/[slug]: /blog/first')
     expect(stderr).toContain('/blog/[slug]: /blog/second')
+    expect(stderr).toContain('/custom-error')
+    expect(stderr).toContain('custom error message')
   })
 })