unexpected CAST result

SET @aaa = COLUMN_CREATE('price', '');

SELECT COLUMN_GET(@aaa, 'price' AS DECIMAL) aaa;

aaa     

--------

0       

SELECT COLUMN_GET(@aaa, 'price' AS DECIMAL)  + 1 aaa

aaa     

--------

1       

DELIMITER $$

CREATE FUNCTION `test`(

    par_aaa DECIMAL(10,2)

   )

    RETURNS DECIMAL(10,2)

    DETERMINISTIC    

    BEGIN

	RETURN 0;

    END$$

DELIMITER ;

SELECT test(COLUMN_GET(@aaa, 'price' AS DECIMAL)) bbb

Error CODE: 1918

Encountered illegal VALUE '' WHEN converting TO DECIMAL

SELECT test('') bbb

Error CODE: 1366

Incorrect DECIMAL VALUE: '' FOR COLUMN 'par_aaa' AT ROW 441

SELECT test(CAST('' AS DECIMAL(10,2))) bbb

Error CODE: 1292

Truncated incorrect DECIMAL VALUE: ''

SELECT test(''+0) bbb

bbb     

--------

0.00   

SELECT @@sql_mode

NO_BACKSLASH_ESCAPES,STRICT_ALL_TABLES,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION