[PDI-9989] MongoDB Output Step throws ArrayIndexOutOfBounds when input
field is missing. Junit test added
modified:   test-src/org/pentaho/di/trans/steps/mongodboutput/MongoDbOutputTest.java
[PDI-9989] MongoDB Output Step throws ArrayIndexOutOfBounds when input
field is missing. Fix added.
modified:   src/org/pentaho/di/trans/steps/mongodboutput/MongoDbOutput.java
modified:   src/org/pentaho/di/trans/steps/mongodboutput/messages/messages_en_US.properties