ndb - fix ha_ndb crash on ordered index on nullable varchar

mysql-test/r/ndb_index_ordered.result:
  fix ha_ndb crash on ordered index on nullable varchar
mysql-test/t/ndb_index_ordered.test:
  fix ha_ndb crash on ordered index on nullable varchar
sql/ha_ndbcluster.cc:
  fix ha_ndb crash on ordered index on nullable varchar

mysql-test/r/ndb_index_ordered.result

@@ -652,3 +652,9 @@ show tables;
 Tables_in_test
 t1
 drop table t1;
+create table t1 (a int, c varchar(10),
+primary key using hash (a), index(c)) engine=ndb;
+insert into t1 (a, c) values (1,'aaa'),(3,'bbb');
+select count(*) from t1 where c<'bbb';
+count(*)
+1

mysql-test/t/ndb_index_ordered.test

@@ -349,4 +349,10 @@ select a from t1 where b = 2;
 show tables;
 drop table t1;
 
+# mysqld 5.0.13 crash, no bug#
+create table t1 (a int, c varchar(10),
+  primary key using hash (a), index(c)) engine=ndb;
+insert into t1 (a, c) values (1,'aaa'),(3,'bbb');
+select count(*) from t1 where c<'bbb';
+
 # End of 4.1 tests

sql/ha_ndbcluster.cc

@@ -1214,7 +1214,7 @@ inline ulong ha_ndbcluster::index_flags(uint idx_no, uint part,
 
 static void shrink_varchar(Field* field, const byte* & ptr, char* buf)
 {
-  if (field->type() == MYSQL_TYPE_VARCHAR) {
+  if (field->type() == MYSQL_TYPE_VARCHAR && ptr != NULL) {
     Field_varstring* f= (Field_varstring*)field;
     if (f->length_bytes == 1) {
       uint pack_len= field->pack_length();