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/pipeline/document_source_query_stats.h:85: UNINIT_CTOR 170751 Class member declaration for "_transformIdentifiers".
/src/mongo/db/pipeline/document_source_query_stats.h:54: UNINIT_CTOR 170751 Non-static class member "_transformIdentifiers" is not initialized in this constructor nor in any functions that it calls.