So, if you receive ERROR you want to check if there is already an error stored in the map, and if not, add it? You can use the Standard std::map functions:
• count to check if this element is already in the map http://www.cplusplus.com/reference/map/map/count/
• find to find it http://www.cplusplus.com/reference/map/map/find/
• insert to add a new one http://www.cplusplus.com/reference/map/map/insert/