[PATCH] Bug#26793 I_S query crashes in NDB

If ::exteral_lock hadn't been called, we'd have no NDB object,
so need to check/get one here.

It looks like sql_show.cc is the only place that does this....
or at least the other places will be well hidden.

Index: ndb-work/sql/ha_ndbcluster.cc
===================================================================

sql/ha_ndbcluster.cc

@@ -3310,6 +3310,8 @@ int ha_ndbcluster::info(uint flag)
     DBUG_PRINT("info", ("HA_STATUS_AUTO"));
     if (m_table && table->found_next_number_field)
     {
+      if ((my_errno= check_ndb_connection()))
+        DBUG_RETURN(my_errno);
       Ndb *ndb= get_ndb();
       
       Uint64 auto_increment_value64;