[CBRD-24780] An error occurs when casting an empty string to bigint.

[youngjinj]

http://jira.cubrid.org/browse/CBRD-24780

For backwards compatibility, casting from empty string to bigint is allowed.

select cast ('' as bigint);

/* AS-IS */
ERROR: Cannot coerce value of domain "character" to domain "bigint".

/* TO-BE */
<00001>  cast('' as bigint): 0