Fixed a rare bug when fulltext index is present and no tables are used.

A better fix would be to have a map of tables that are not used at all, 
and to annul just fledls in that TABLE.

Docs/manual.texi

@@ -49457,6 +49457,8 @@ Our TODO section contains what we plan to have in 4.0. @xref{TODO MySQL 4.0}.
 
 @itemize @bullet
 @item
+Fixed a rare bug when fulltext index is present and no tables are used
+@item
 Added privileges @strong{create temporary table}, @strong{lock tables},
 @strong{replication client}, @strong{replication slave},
 @strong{show databases} and @strong{super}. To use these, you must have

mysql-test/r/fulltext.result

@@ -192,3 +192,12 @@ a	b
 2	fullaaa fullzzz
 1	I wonder why the fulltext index doesnt work?
 drop table t1;
+CREATE TABLE t1 ( id int(11) NOT NULL auto_increment primary key, mytext text NOT NULL, FULLTEXT KEY mytext (mytext)) TYPE=MyISAM;
+INSERT INTO t1 VALUES (1,'my small mouse'),(2,'la-la-la'),(3,'It is so funny'),(4,'MySQL Tutorial');
+select 8 from t1;
+8
+8
+8
+8
+8
+drop table t1;

mysql-test/t/fulltext.test

@@ -154,4 +154,8 @@ insert into t1 values (2,"fullaaa fullzzz");
 select * from t1 where match b against ('full*' in boolean mode);
 
 drop table t1;
+CREATE TABLE t1 ( id int(11) NOT NULL auto_increment primary key, mytext text NOT NULL, FULLTEXT KEY mytext (mytext)) TYPE=MyISAM;
+INSERT INTO t1 VALUES (1,'my small mouse'),(2,'la-la-la'),(3,'It is so funny'),(4,'MySQL Tutorial');
+select 8 from t1;
+drop table t1;
 

sql/sql_select.cc

@@ -257,7 +257,14 @@ mysql_select(THD *thd,TABLE_LIST *tables,List<Item> &fields,COND *conds,
     }
     TABLE_LIST *table;
     for (table=tables ; table ; table=table->next)
+    {
       join.tables++;
+      if (!thd->used_tables)
+      {
+	TABLE *tbl=table->table;
+	tbl->keys_in_use_for_query=tbl->used_keys= tbl->keys_in_use=0;
+      }
+    }
   }
   procedure=setup_procedure(thd,proc_param,result,fields,&error);
   if (error)