SELECT NULL fails with MT_DOP > 0

set mt_dop=1;
select null;

F1025 17:21:33.506001 18517 simple-scheduler.cc:433] Check failed: !ContainsNode(fragment.plan, TPlanNodeType::UNION_NODE) 

#7  0x00000000013f46b2 in impala::SimpleScheduler::MtComputeFragmentExecParams (this=0xbe0b340, 
    plan_exec_info=..., fragment_params=0xc2de580, schedule=0xdc9e1c0)
    at /home/abehm/impala/be/src/scheduling/simple-scheduler.cc:433
#8  0x00000000013f3f3f in impala::SimpleScheduler::MtComputeFragmentExecParams (this=0xbe0b340, 
    schedule=0xdc9e1c0) at /home/abehm/impala/be/src/scheduling/simple-scheduler.cc:378
#9  0x00000000013f7629 in impala::SimpleScheduler::Schedule (this=0xbe0b340, schedule=0xdc9e1c0)
    at /home/abehm/impala/be/src/scheduling/simple-scheduler.cc:888
#10 0x00000000014cc4a4 in impala::ImpalaServer::QueryExecState::ExecQueryOrDmlRequest (this=0xc3be000, 
    query_exec_request=...) at /home/abehm/impala/be/src/service/query-exec-state.cc:444
#11 0x00000000014c93f3 in impala::ImpalaServer::QueryExecState::Exec (this=0xc3be000, 
    exec_request=0x7fd894788880) at /home/abehm/impala/be/src/service/query-exec-state.cc:154
#12 0x000000000145743e in impala::ImpalaServer::ExecuteInternal (this=0xc28a400, query_ctx=..., 
    session_state=std::shared_ptr (count 6, weak 0) 0xbb44900, registered_exec_state=0x7fd894789f2f, 
    exec_state=0x7fd89478a2c0) at /home/abehm/impala/be/src/service/impala-server.cc:817
#13 0x0000000001456c6a in impala::ImpalaServer::Execute (this=0xc28a400, query_ctx=0x7fd894789fc0, 
    session_state=std::shared_ptr (count 6, weak 0) 0xbb44900, exec_state=0x7fd89478a2c0)
    at /home/abehm/impala/be/src/service/impala-server.cc:764
#14 0x00000000014be211 in impala::ImpalaServer::query (this=0xc28a400, query_handle=..., query=...)
    at /home/abehm/impala/be/src/service/impala-beeswax-server.cc:66