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/bson/util/bsoncolumnbuilder.h:179: UNINIT_CTOR 121945 Class member declaration for "_referenceSubObjType".
/src/mongo/bson/util/bsoncolumnbuilder.cpp:513: UNINIT_CTOR 121945 Non-static class member "_referenceSubObjType" is not initialized in this constructor nor in any functions that it calls.