Bug#19564: mysql displays NULL instead of space

Correct a bug (that I introduced, after using Oracle's database software for 
too many years) where the length of the database-sent data is incorrectly 
used to infer NULLness.

client/mysql.cc

@@ -2319,7 +2319,7 @@ print_table_data(MYSQL_RES *result)
       uint extra_padding;
 
       /* If this column may have a null value, use "NULL" for empty.  */
-      if (! not_null_flag[off] && (lengths[off] == 0))
+      if (! not_null_flag[off] && (cur[off] == NULL))
       {
         buffer= "NULL";
         data_length= 4;

mysql-test/r/mysql.result

@@ -74,7 +74,7 @@ c_cp932
 +----------------------+------------+--------+
 | >a   <               | b          | 123421 | 
 | >a   <               | 0123456789 |      4 | 
-| >abcd<               | NULL       |      4 | 
+| >abcd<               |            |      4 | 
 +----------------------+------------+--------+
 +------+------+---------------------------+
 | i    | j    | k                         |
@@ -94,6 +94,14 @@ c_cp932
 | Field | Type    | Null | Key | Default | Extra |
 +-------+---------+------+-----+---------+-------+
 | i     | int(11) | YES  |     | NULL    |       | 
-| j     | int(11) | NO   |     | NULL    |       | 
+| j     | int(11) | NO   |     |         |       | 
 | k     | int(11) | YES  |     | NULL    |       | 
 +-------+---------+------+-----+---------+-------+
++------+------+
+| i    | s1   |
++------+------+
+|    1 | x    | 
+|    2 | NULL | 
+|    3 |      | 
++------+------+
+End of 5.0 tests

mysql-test/t/mysql.test

@@ -72,3 +72,11 @@ drop table t1;
 #
 --exec $MYSQL -t --default-character-set utf8 test -e "create table t1 (i int, j int not null, k int); insert into t1 values (null, 1, null); select * from t1; describe t1; drop table t1;"
 
+#
+# Bug#19564: mysql displays NULL instead of space
+#
+--exec $MYSQL -t test -e "create table b19564 (i int, s1 char(1)); insert into b19564 values (1, 'x'); insert into b19564 values (2, NULL); insert into b19564 values (3, ' '); select * from b19564 order by i; drop table b19564;" 
+
+--echo End of 5.0 tests
+
+