Coverity analysis defect 56350: Dereference null return value

A new defect has been detected and assigned to geert.bosch in Coverity Connect.
http://coverity.mongodb.com//sourcebrowser.htm?projectId=10001#mergedDefectId=56350
The defect was flagged by checker NULL_RETURNS in
file /src/mongo/db/commands/mr.cpp
function mongo::mr::State::postProcessCollectionNonAtomic(mongo::OperationContext *, mongo::CurOp *, mongo::ProgressMeterHolder &)
and this ticket was created by milkie