Spark handles 'NaN' as 0 in sums

Currently, Spark handles 'NaN' as 0 in window functions, such that 3+'NaN'=3. PgSQL, on the other hand, handles the entire result as 'NaN', as in 3+'NaN' = 'NaN'

I experienced this with the query below:

SELECT a, b,
       SUM(b) OVER(ORDER BY A ROWS BETWEEN 1 PRECEDING AND CURRENT ROW)
FROM (VALUES(1,1),(2,2),(3,(cast('nan' as int))),(4,3),(5,4)) t(a,b);