[ntuple] fix virtual destructor visibility

Author: jblomer

tree/ntuple/inc/ROOT/RField/RFieldFundamental.hxx

@@ -412,14 +412,13 @@ protected:
       fPrincipalColumn = fAvailableColumns[0].get();
    }
 
-   ~RRealField() override = default;
-
 public:
    using Base::SetColumnRepresentatives;
 
    RRealField(std::string_view name, std::string_view typeName) : RSimpleField<T>(name, typeName) {}
    RRealField(RRealField &&other) = default;
    RRealField &operator=(RRealField &&other) = default;
+   ~RRealField() override = default;
 
    /// Sets this field to use a half precision representation, occupying half as much storage space (16 bits:
    /// 1 sign bit, 5 exponent bits, 10 mantissa bits) on disk.

tree/ntuple/inc/ROOT/RFieldVisitor.hxx

@@ -56,6 +56,8 @@ As an example of a concrete use case, see Internal::RPrintSchemaVisitor.
 // clang-format on
 class RFieldVisitor {
 public:
+   virtual ~RFieldVisitor() = default;
+
    virtual void VisitField(const ROOT::RFieldBase &field) = 0;
    virtual void VisitFieldZero(const ROOT::RFieldZero &field) { VisitField(field); }
    virtual void VisitArrayField(const ROOT::RArrayField &field) { VisitField(field); }