The gallery thumbnail endpoint was returning 404 when thumbnail_path
was null or the file didn't exist, unlike the admin endpoint which
generates thumbnails on demand using ensureThumbnail().
- Import ensureThumbnail from imageProcessor
- Use ensureThumbnail() in gallery thumbnail route to generate
thumbnails on demand if they don't exist
- This matches the admin endpoint behavior
Fixes#96
Paul Nothaft
e3c3c4c951