if no value set for a choose, display no value

tiramisu_cmdline_parser/api.py

@@ -114,6 +114,7 @@ class TiramisuNamespace(Namespace):
         except ValueError as err:
             if option.option.type() == 'choice':
                 values = option.value.list()
+                display_value = ''
                 if isinstance(true_value, list):
                     for val in value:
                         if val not in values: