Broken type checking for empty subqueries

Hello,

after upgrade from PG11 to PG14.8 the following statement started failing:

select
     a::BIGINT
FROM (
     SELECT
         '$maybeNumber'::VARCHAR AS a
     WHERE NOT '$maybeNumber' LIKE '%maybeNumber'
) AS foo;

Expected (as in PG11): The query should return empty result with one column.
Actual:  SQL Error [22P02]: ERROR: invalid input syntax for type bigint: 
"$maybeNumber".

Where is a workaround that shows the behavior is quite non-stable. 
Following passes normally while still using the same subquery with one 
more empty result from another one:

select
     a::BIGINT
FROM (
     SELECT
         '$maybeNumber'::VARCHAR AS a
     WHERE NOT '$maybeNumber' LIKE '%maybeNumber'
     UNION
     SELECT '0' AS a WHERE false
) AS foo;

Thanks all for the great work you do on PG.
Marek Malevic