added virtual destructors to multipliers

src/storm/solver/GmmxxMultiplier.h

@@ -19,6 +19,7 @@ namespace storm {
         class GmmxxMultiplier : public Multiplier<ValueType> {
         public:
             GmmxxMultiplier(storm::storage::SparseMatrix<ValueType> const& matrix);
+            virtual ~GmmxxMultiplier() = default;
             
             virtual void multiply(Environment const& env, std::vector<ValueType> const& x, std::vector<ValueType> const* b, std::vector<ValueType>& result) const override;
             virtual void multiplyGaussSeidel(Environment const& env, std::vector<ValueType>& x, std::vector<ValueType> const* b) const override;

src/storm/solver/Multiplier.h

@@ -23,6 +23,8 @@ namespace storm {
             
             Multiplier(storm::storage::SparseMatrix<ValueType> const& matrix);
             
+            virtual ~Multiplier() = default;
+            
             /*
              * Clears the currently cached data of this multiplier in order to free some memory.
              */

src/storm/solver/NativeMultiplier.h

@@ -16,6 +16,7 @@ namespace storm {
         class NativeMultiplier : public Multiplier<ValueType> {
         public:
             NativeMultiplier(storm::storage::SparseMatrix<ValueType> const& matrix);
+            virtual ~NativeMultiplier() = default;
             
             virtual void multiply(Environment const& env, std::vector<ValueType> const& x, std::vector<ValueType> const* b, std::vector<ValueType>& result) const override;
             virtual void multiplyGaussSeidel(Environment const& env, std::vector<ValueType>& x, std::vector<ValueType> const* b) const override;