Don't return an empty object that would then be stored as the user, but (#650)

instead return null which is then easier to catch (as the code already
expects to receive)

lib/user.js

@@ -44,7 +44,8 @@ async function get(
     }
     return json
   } catch (err) {
-    return {}
+    console.error(err.stack)
+    return null
   }
 }