NULL's operator "<=>" get wrong result

[chenhao7253886]

now , the result of comparing null with other value by operator "<=>" is wrong, for example:
mysql> select null <=> null;
+-------------+
| NULL = NULL |
+-------------+
| NULL |
+-------------+
1 row in set (0.00 sec)
the result is wrong, the right result is:
mysql> select null <=> null;
+-------------+
| NULL = NULL |
+-------------+
| 1 |
+-------------+
1 row in set (0.01 sec)
Operator "<=>" is safe for null's comparing，so it will return 1 or 0. This operator is the same as "=" operator when comparing non-null value, but it will return 1 or 0 for comparing "null" with "null" or other non-null value.