Added a convert<> specialization for YAML::_Null (so you can say node[YAML::Null])

include/yaml-cpp/node/detail/impl.h

@@ -132,6 +132,7 @@ namespace YAML
 		inline node& node_data::convert_to_node(const T& rhs, shared_memory_holder pMemory)
 		{
 			Node value = convert<T>::encode(rhs);
+			value.EnsureNodeExists();
 			pMemory->merge(*value.m_pMemory);
 			return *value.m_pNode;
 		}