group photo upload: respond 500 on DB error instead of hanging (async throw in express4)

server.js

@@ -826,7 +826,8 @@ app.post('/api/groups/:id/photos', requireAdmin, (req, res, next) => {
     res.status(201).json(rows[0]);
   } catch (e) {
     safeUnlink(`uploads/${req.file.filename}`);
-    throw e;
+    console.error('POST /api/groups/:id/photos:', e);
+    res.status(500).json({ error: e.message });
   }
 });