heap-use-after-free in heap_rnext with tree indexes

CREATE TABLE t1 (

    k INT,

    pad VARCHAR(200),

    INDEX idx USING BTREE (k)

) ENGINE=MEMORY;

INSERT INTO t1 (k, pad) VALUES

  (10,'a'),(20,'b'),(30,'c'),(40,'d'),(50,'e'),

  (60,'f'),(70,'g'),(80,'h'),(90,'i'),(100,'j'),

  (110,'k'),(120,'l'),(130,'m'),(140,'n'),(150,'o'),

  (160,'p'),(170,'q'),(180,'r'),(190,'s'),(200,'t');

HANDLER t1 OPEN;

HANDLER t1 READ idx FIRST;

HANDLER t1 READ idx NEXT;

HANDLER t1 READ idx NEXT;

HANDLER t1 READ idx NEXT;

HANDLER t1 READ idx NEXT;

UPDATE t1 SET k = k + 5000 WHERE k BETWEEN 20 AND 180;

HANDLER t1 READ idx NEXT;

DROP TABLE t1;