Deal with unknown values for device partition properties in dump-properties.

examples/dump-properties.py

@@ -19,7 +19,8 @@ def print_info(obj, info_cls):
             if (info_cls == cl.device_info and info_name == "PARTITION_TYPES_EXT"
                     and isinstance(info_value, list)):
                 print("%s: %s" % (info_name, [
-                    cl.device_partition_property_ext.to_string(v) for v in info_value]))
+                    cl.device_partition_property_ext.to_string(v,
+                        "<unknown device partition property %d>") for v in info_value]))
             else:
                 print("%s: %s" % (info_name, info_value))