JSON_MERGE returns nullwhen merging empty array

 SELECT JSON_MERGE('[1]', '[]');

+-------------------------+

| JSON_MERGE('[1]', '[]') |

+-------------------------+

| NULL                    |

+-------------------------+

1 row in set, 1 warning (0.00 sec)

SHOW WARNINGS;

+---------+------+--------------------------------------------------------------------------------+

| Level   | Code | Message                                                                        |

+---------+------+--------------------------------------------------------------------------------+

| Warning | 4038 | Syntax error in JSON text in argument 1 to function 'json_merge' at position 5 |

+---------+------+--------------------------------------------------------------------------------+

 SELECT JSON_MERGE('[1]', '[]');

+-------------------------+

| JSON_MERGE('[1]', '[]') |

+-------------------------+

| [1]                    |

+-------------------------+