https://jira.mongodb.org/browse/JAVA-863, fixed null checks in reove method
https://jira.mongodb.org/browse/JAVA-863, fixed null checks in remove method
Merge branch 'master' of https://github.com/neerajbhatt/mongo-java-driver into 2x-863

Conflicts:
	src/test/com/mongodb/gridfs/GridFSTest.java