bugfix for 'ANALYZE for MERGE' and table-less MERGE table

mysql-test/r/merge.result:
  test added
mysql-test/t/merge.test:
  test added

mysql-test/r/merge.result

@@ -258,7 +258,7 @@ t3	CREATE TABLE `t3` (
   `othr` int(11) NOT NULL default '0'
 ) TYPE=MRG_MyISAM UNION=(t1,t2)
 drop table t3,t2,t1;
-create table t1 (a int not null) type=merge;
+create table t1 (a int not null, key(a)) type=merge;
 select * from t1;
 a
 drop table t1;

mysql-test/t/merge.test

@@ -105,7 +105,7 @@ drop table t3,t2,t1;
 #
 # Test table without unions
 #
-create table t1 (a int not null) type=merge;
+create table t1 (a int not null, key(a)) type=merge;
 select * from t1;
 drop table t1;
 

sql/ha_myisammrg.cc

@@ -231,7 +231,7 @@ void ha_myisammrg::info(uint flag)
 #endif
   if (flag & HA_STATUS_CONST)
   {
-    if (table->key_parts)
+    if (table->key_parts && info.rec_per_key)
       memcpy((char*) table->key_info[0].rec_per_key,
 	     (char*) info.rec_per_key,
 	     sizeof(table->key_info[0].rec_per_key)*table->key_parts);