Dictionary better error message during attribute parsing

src/Dictionaries/DictionaryStructure.cpp

@@ -344,7 +344,9 @@ std::vector<DictionaryAttribute> DictionaryStructure::getAttributes(
             }
             catch (Exception & e)
             {
-                e.addMessage("error parsing null_value");
+                String dictionary_name = config.getString(".dictionary.name", "");
+                e.addMessage("While parsing null_value for attribute with name " + name
+                    + " in dictionary " + dictionary_name);
                 throw;
             }
         }