It should be impossible since your Ranger has more than 12 UL. Then again technically the Vampire can't lose either. I would have thought this would crash the game since it would be impossible for either unit to get a hit.
Due to the structure of how maps are saved thats a bit hard to do at the moment. If you know any map that has this issue, please give me the mapID/link to the map and I´ll fix it.
You may add a line to the code making it autowin if Hero UL is above the dice limit. So even if mapeditor makes a mistake if will corrected in most cases.