I re-created a minimalistic example that produces the problem:

var mongoDB = require('mongodb');

var randomIdentifier = 'Demo'+Math.random().toString(36).slice(-8);

try
{
mongoDB.MongoClient.connect("mongodb://localhost:27017/"+randomIdentifier,

{native_parser:true}

, function(err, db) {
if(err)

{ console.log(err); }

db.close(function(err, result) {
if(err)

{ console.log(err); }

db.createCollection('nonexistent',

{'w':1}

, function(err, collection) {
if(err)

{ console.log('will never get here'); console.log(err); }

else

{ console.log('or here'); }

})
});
});
}
catch(err)

{ console.log("or here for that matter"); }