LOAD DATA INFILE doesn't read NULL values accurately

SET SESSION sql_mode = "NO_BACKSLASH_ESCAPES";

SELECT NULL, 0, '' INTO OUTFILE 'data-server.csv';

CREATE

OR REPLACE TABLE loading (col1 VARCHAR(255) NULL, col2 INT, col3 VARCHAR(255));

LOAD DATA LOCAL INFILE 'data-server.csv' INTO TABLE loading;

SELECT

   *

FROM

   loading

WHERE

   col1 IS NULL;