DECLARE CURSOR: "Memory not freed: 280 bytes lost" on syntax error

This test script:

DELIMITER $$;

--error ER_PARSE_ERROR

BEGIN NOT ATOMIC

  DECLARE cur CURSOR (a INT) FOR SELECT a+1;

  OPEN cur(sp_followed_by_syntax_error();

  CLOSE cur;

END;

$$

DELIMITER ;$$

makes MTR complain about a memory leak:

Warning: 280 bytes lost at 0x7fe82800aba0, allocated by T@0 at mysys/array.c:72, mysys/hash.c:99, sql/sp.cc:2331, sql/sp.cc:2646, sql/item_create.cc:2631, sql/item_create.cc:2477, sql/sql_yacc.yy:10752, sql/sql_parse.cc:10456
Warning: 280 bytes lost at 0x7fe82800aba0, allocated by T@0 at mysys/array.c:72, mysys/hash.c:99, sql/sp.cc:2331, sql/sp.cc:2646, sql/item_create.cc:2631, sql/item_create.cc:2477, sql/sql_yacc.yy:10752, sql/sql_parse.cc:10456

This is a similar problem to MDEV-30680, but the parse error happens in a different syntax context.

The problem happens in the 10.5 tree with MDEV-30680 already pushed.