MongoEngine/mongoengine — pull request #655 by jonathansp (2014-05-27 19:40:14+00:00)
Title: Avoid to open all documents from cursors in an if stmt

Using a cursos in an if statement:

cursor = Collection.objects

if cursor:
(...)

Will open all documents, because there are not an __nonzero__ method.
This change check only one document (if present) and returns True or False.