BUG#47838, NULL values in ranges was dropped due to missing else part in...

BUG#47838, NULL values in ranges was dropped due to missing else part in store_tuple_to_record, added more tests

mysql-test/r/partition_column.result

 drop table if exists t1;
 create table t1 (a int signed)
+partition by list (a)
+( partition p0 values in (1, 3, 5, 7, 9, NULL),
+partition p1 values in (2, 4, 6, 8, 0));
+insert into t1 values (NULL),(0),(1),(2),(2),(4),(4),(4),(8),(8);
+select * from t1 where NULL <= a;
+a
+select * from t1 where a is null;
+a
+NULL
+explain partitions select * from t1 where a is null;
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	p0	ALL	NULL	NULL	NULL	NULL	10	Using where
+select * from t1 where a <= 1;
+a
+1
+0
+drop table t1;
+create table t1 (a int signed)
 partition by list column_list(a)
 ( partition p0 values in (column_list(1), column_list(3), column_list(5),
 column_list(7), column_list(9), column_list(NULL)),
 partition p1 values in (column_list(2), column_list(4), column_list(6),
 column_list(8), column_list(0)));
 insert into t1 values (NULL),(0),(1),(2),(2),(4),(4),(4),(8),(8);
+select * from t1 where a <= NULL;
+a
+select * from t1 where a is null;
+a
+NULL
+explain partitions select * from t1 where a is null;
+id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	p0	ALL	NULL	NULL	NULL	NULL	2	Using where
 select * from t1 where a <= 1;
 a
 1