Cannot getting empty result in case

I found the answer:
https://stackoverflow.com/questions/56372462/how-to-get-empty-result-set-with-a-case-statement

The query gives correct results:

dbadmin=> SELECT CASE WHEN ('test' IS NULL) THEN (SELECT 'null_result') ELSE (SELECT 'empty_result' WHERE 1<>1) END;
 case
------

(1 row)

dbadmin=> SELECT CASE WHEN ('test' IS NULL) THEN (SELECT 'null_result') ELSE (SELECT 'empty_result' WHERE 1=1) END;
     case
--------------
 empty_result
(1 row)