Problem: Vim9: null_object and null_class are no reserved names
Solution: Add null_object and null_class as reserved names.
(Yegappan Lakshmanan)
closes: #17054
Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>