Fixed bug: load table from master w/empty master would hang.

Now it properly returns error.
Added respective test case.

mysql-test/r/rpl_empty_master_crash.result

+slave stop;
+reset master;
+reset slave;
+drop table if exists t1,t2,t3,t4,t5,t6,t7,t8,t9;
+slave start;
+use test;
+drop table if exists t1;
+show slave status;
+Master_Host	Master_User	Master_Port	Connect_retry	Master_Log_File	Read_Master_Log_Pos	Relay_Log_File	Relay_Log_Pos	Relay_Master_Log_File	Slave_IO_Running	Slave_SQL_Running	Replicate_do_db	Replicate_ignore_db	Last_errno	Last_error	Skip_counter	Exec_master_log_pos	Relay_log_space
+		0	0		0		0		No	No			0		0	0	0
+load table t1 from master;
+Error in fetch_master_table

mysql-test/t/rpl_empty_master_crash.test

+source include/master-slave.inc;
+connection master;
+use test;
+drop table if exists t1;
+show slave status;
+--error 1218
+load table t1 from master;

sql/repl_failsafe.cc

@@ -608,6 +608,9 @@ int show_slave_hosts(THD* thd)
 
 int connect_to_master(THD *thd, MYSQL* mysql, MASTER_INFO* mi)
 {
+  if (!mi->host || !*mi->host)			/* empty host */
+    return 1;
+
   if (!mc_mysql_connect(mysql, mi->host, mi->user, mi->password, 0,
 		   mi->port, 0, 0))
   {