NODE-4609 Description
Version 4.9.1

When the first element of result of find().map().toArray() is falsy value (e.g. false, 0), then it will be removed ([0,0,1] --> [0,1]).

Also, one null value from the start will be removed ([null, 1] --> [1]), and sequence of null from the start will result an empty array ([null, null, 1] --> []).

This just happened on Node.js Driver. find().map() in MongoDB shell will return all results.