Python vibe coding IDE fix (#1268)

### Description

Small bugfix for build

### Demo URL

### Type of Change

- [ ] New Example
- [x] Example updates (Bug fixes, new features, etc.)
- [ ] Other (changes to the codebase, but not to examples)

### New Example Checklist

- [ ] 🛫 `npm run new-example` was used to create the example
- [ ] 📚 The template wasn't used but I carefuly read the [Adding a new
example](https://github.com/vercel/examples#adding-a-new-example) steps
and implemented them in the example
- [ ] 📱 Is it responsive? Are mobile and tablets considered?

Author: ricardo-agz

python/vibe-coding-ide/frontend/src/app/App.tsx

@@ -380,7 +380,7 @@ function App() {
                   projects.find((p) => p.id === activeProjectId)?.name ||
                   'project'
                 ).replace(/\s+/g, '_')
-                const folder = zip.folder(rootName)
+                const folder = zip.folder(rootName) ?? zip
                 // Include all current project files; proposals are suggestions only
                 Object.entries(project).forEach(([path, content]) => {
                   const normalized = (path || '').replace(/^\//, '')