Uninitialized scalar field

The field will contain an arbitrary value left over from earlier computations. A scalar field is not initialized by the constructor
/src/mongo/db/s/start_chunk_clone_request.h:140: UNINIT_CTOR 115245 Class member declaration for "_txnNumber".
/src/mongo/db/s/start_chunk_clone_request.cpp:61: UNINIT_CTOR 115245 Non-static class member "_txnNumber" is not initialized in this constructor nor in any functions that it calls.