When executing GROUP BY NULL, Mariadb returns unexpected results

CREATE TABLE t0 (
c0 double unsigned zerofill NULL
);
CREATE TABLE t0 (
c0 double unsigned NULL
);

INSERT INTO t0 VALUES (0.1251773127435537), (NULL), (0), (0.6665588482250941);

CREATE TABLE t1(c0 BOOL);

INSERT INTO t1 VALUES (NULL), (NULL), (0), (0);

SELECT t0.c0 FROM t0 NATURAL RIGHT JOIN t1 GROUP BY NULL;

Expected:
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Result:
MariaDB> SELECT t0.c0 FROM t0 NATURAL RIGHT JOIN t1 GROUP BY NULL;
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1 row in set (0.000 sec)