removed the value field from attribute_definition because it's a definition and should not hold a value.

source/orm/sql/connection.cpp

@@ -229,7 +229,7 @@ utils::result<std::unique_ptr<statement_impl>, utils::error> connection::perform
           [&col](const auto &value) { return value.name() == col.name(); }
         );
         if (col.type() == utils::basic_type::type_null && rit != result->end()) {
-          const_cast<object::attribute_definition&>(col).type(rit->type());
+          const_cast<object::attribute_definition&>(col).change_type(rit->type());
         }
       }
     }