in DataForm, a field of type 'list-single' can have no <value> element. Create a default one in such a case to prevent TB

src/common/connection.py

@@ -1245,6 +1245,8 @@ class Connection:
 					for tag in tags:
 						dic[i]['options'][j]['values'].append(tag.getData())
 					j += 1
+				if not dic[i].has_key('values'):
+					dic[i]['values'] = [dic[i]['options'][0]['values'][0]]
 			i += 1
 		return dic