fix backend bug again

test-len.js

@@ -0,0 +1,10 @@
+const errs = [
+  "Table 'nutrition.users' doesn't exist",
+  "connect ECONNREFUSED 172.18.0.2:3306",
+  "connect ECONNREFUSED db:3306",
+  "Unknown database 'nutrition'"
+];
+errs.forEach(e => {
+  const json = JSON.stringify({ error: e });
+  console.log(Buffer.byteLength(json), json);
+});