Unexpected Results by not_null_range_scan

By changing the setting: not_null_range_scan, a query returns different results shown as follows.

CREATE TABLE t0(c0 CHAR UNIQUE);
INSERT INTO t0 VALUES (DEFAULT);

SET SESSION optimizer_switch = 'not_null_range_scan=off';
SELECT c0 FROM t0 WHERE (TRUE NOT IN (LOCATE(1, false, c0))); –

SET SESSION optimizer_switch = 'not_null_range_scan=on';
SELECT c0 FROM t0 WHERE (TRUE NOT IN (LOCATE(1, false, c0))); – {}