Location of bug:
https://www.google.com/url?q=https%3A%2F%2Fgithub.com%2Fmongodb%2Fmongo-cxx-driver%2Fblob%2F2af5d5ae336b3ebd4dbd50367e7df04361a626b7%2Fsrc%2Fmongo%2Fbson%2Fbsonelement.cpp%23L583&sa=D&sntz=1&usg=AFQjCNHKcPopXrCxua3WkC4PO_VZA_IP5w

I originally posted to the mongodb-users google group with the issue:
https://groups.google.com/forum/#!topic/mongodb-user/8CueGyVIkTY