As shown in the screenshot attached, I have a collection called Authors.

I'm accessing a collection from Node.js using the following JavaScript call.

Today, I have experienced "UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'collection' of undefined"

with the line theDB.collection(COLL_AUTHORS) once. Only once so far.

I cannot reproduce this error, but just a concern why the mongDB fails to recognize the existing collecton?  What is the best way to handle this kind of random error?

```
const COLL_AUTHORS = "Authors"
let MongoClient = require('mongodb').MongoClient
let queryAuthorByUid = async (uidString) => {
  console.log('queryAuthorByUidAsync : '+uidString)
  const authors=theDB.collection(COLL_AUTHORS)
  // find by uid
  var who=awaitauthors.findOne({userid:uidString})
  console.log('found author 'uidString'? = '+who)
  return who
}
```