fix nullable autoinc test w/o versioning

mysql-test/suite/versioning/r/alter.result

@@ -398,6 +398,16 @@ t	CREATE TABLE `t` (
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1
 call verify_vtq;
 No	A	B	C	D
+create or replace table t (a int);
+insert t values (1),(2),(3),(4);
+alter table t add b int auto_increment null unique;
+select * from t;
+a	b
+1	1
+2	2
+3	3
+4	4
+drop table t;
 create or replace table t (a int) with system versioning engine=innodb;
 insert into t values (1), (2), (3);
 delete from t where a<3;

mysql-test/suite/versioning/t/alter.test

@@ -205,6 +205,13 @@ alter table t drop system versioning, algorithm=copy;
 show create table t;
 call verify_vtq;
 
+# nullable autoinc test w/o versioning
+create or replace table t (a int);
+insert t values (1),(2),(3),(4);
+alter table t add b int auto_increment null unique;
+select * from t;
+drop table t;
+
 create or replace table t (a int) with system versioning engine=innodb;
 insert into t values (1), (2), (3);
 delete from t where a<3;

sql/handler.cc

@@ -3071,8 +3071,8 @@ int handler::update_auto_increment()
         table->next_number_field->set_null();
         DBUG_RETURN(0);
       }
-      table->next_number_field->set_notnull();
     }
+    table->next_number_field->set_notnull();
   }
 
   /*