fix mkql build

Author: swalrus1

ydb/library/conclusion/status.h

@@ -3,7 +3,7 @@
 
 namespace NKikimr {
 
-using TConclusionStatus = TConclusionStatusImpl<TNull, TNull{}, TNull{}>;
+using TConclusionStatus = TConclusionStatusImpl<::TNull, ::TNull{}, ::TNull{}>;
 
 template <class TStatus, TStatus StatusOk, TStatus DefaultError>
 using TConclusionSpecialStatus = TConclusionStatusImpl<TStatus, StatusOk, DefaultError>;