Silence deprecation warning when testing element's truth value

This fixes the following deprecation warning, new as of Python 3.12:

DeprecationWarning: Testing an element's truth value will always return True in future versions.

We do want the future behavior here, but since we can't opt into it
cleanly just test vs None explicitly.

generate.py

@@ -52,7 +52,7 @@ def is_descendant_type(types, name, base):
 	if name == base:
 		return True
 	type = types.get(name)
-	if not type:
+	if type is None:
 		return False
 	parents = type.get('parent')
 	if not parents: