Numerous test failures due to NULL dereference in trx_search_latch_if_reserved()

A large number of tests on trunk fail on debug builds. A sample test can be reduced to

--source include/have_innodb.inc

connect (a,localhost,root,,);
connect (b,localhost,root,,);

CREATE TABLE bug47622(
 `rule_key` int(11) NOT NULL DEFAULT '0'
) ENGINE=InnoDB;

connection a;

ALTER TABLE bug47622 ADD UNIQUE IDX_B (rule_key);

DROP TABLE bug47622;

resulting in

Thread 1 (Thread 0x7fe3e2046700 (LWP 16007)):
#0 0x00007fe3ee198f2c in __pthread_kill (threadid=<optimized out>, signo=11) at ../nptl/sysdeps/unix/sysv/linux/pthread_kill.c:62
#1 0x0000000000904455 in my_write_core (sig=11) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/mysys/stacktrace.c:433
#2 0x000000000078587d in handle_fatal_signal (sig=11) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/signal_handler.cc:250
#3 <signal handler called>
#4 0x00000000009a4778 in trx_search_latch_release_if_reserved (trx=0x0) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/storage/innobase/include/trx0trx.ic:36
#5 0x00000000009a4cf3 in innobase_release_temporary_latches (hton=0x32c23f0, thd=0x3b01990) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/storage/innobase/handler/ha_innodb.cc:1139
#6 0x00000000009aa2fa in ha_innobase::open (this=0x7fe3d000ae50, name=0x7fe3d0008448 "./test/bug47622", mode=2, test_if_locked=2) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/storage/innobase/handler/ha_innodb.cc:4738
#7 0x000000000078a2ba in handler::ha_open (this=0x7fe3d000ae50, table_arg=0x7fe3d000a570, name=0x7fe3d0008448 "./test/bug47622", mode=2, test_if_locked=2) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/handler.cc:2346
#8 0x00000000006c0b17 in open_table_from_share (thd=0x3b01990, share=0x7fe3d00080b0, alias=0x7fe3d0004d48 "bug47622", db_stat=39, prgflag=44, ha_open_flags=0, outparam=0x7fe3d000a570, is_create_table=false) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/table.cc:2064
#9 0x00000000005afd92 in open_table (thd=0x3b01990, table_list=0x7fe3d0004d58, mem_root=0x7fe3e2041c90, ot_ctx=0x7fe3e2041c50) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/sql_base.cc:3131
#10 0x00000000005b238f in open_and_process_table (thd=0x3b01990, lex=0x3b036e0, tables=0x7fe3d0004d58, counter=0x7fe3e2041d24, flags=0, prelocking_strategy=0x7fe3e2041f50, has_prelocking_list=false, ot_ctx=0x7fe3e2041c50, new_frm_mem=0x7fe3e2041c90) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/sql_base.cc:4504
#11 0x00000000005b334d in open_tables (thd=0x3b01990, start=0x7fe3e2041d10, counter=0x7fe3e2041d24, flags=0, prelocking_strategy=0x7fe3e2041f50) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/sql_base.cc:5019
#12 0x00000000005b4226 in open_and_lock_tables (thd=0x3b01990, tables=0x7fe3d0004d58, derived=false, flags=0, prelocking_strategy=0x7fe3e2041f50) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/sql_base.cc:5623
#13 0x000000000069aabb in mysql_alter_table (thd=0x3b01990, new_db=0x7fe3d0005280 "test", new_name=0x0, create_info=0x7fe3e20434b0, table_list=0x7fe3d0004d58, alter_info=0x7fe3e20433f0, order_num=0, order=0x0, ignore=false) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/sql_table.cc:6018
#14 0x00000000008d8d35 in Alter_table_statement::execute (this=0x7fe3d0005348, thd=0x3b01990) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/sql_alter.cc:106
#15 0x000000000060e6a0 in mysql_execute_command (thd=0x3b01990) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/sql_parse.cc:4683
#16 0x00000000006113df in mysql_parse (thd=0x3b01990, rawbuf=0x7fe3d0004c30 "ALTER TABLE bug47622 ADD UNIQUE IDX_B (rule_key)", length=48, parser_state=0x7fe3e2045140) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/sql_parse.cc:5924
#17 0x0000000000604957 in dispatch_command (command=COM_QUERY, thd=0x3b01990, packet=0x3b052a1 "ALTER TABLE bug47622 ADD UNIQUE IDX_B (rule_key)", packet_length=48) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/sql_parse.cc:1081
#18 0x0000000000603b4d in do_command (thd=0x3b01990) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/sql_parse.cc:789
#19 0x00000000006f7ab0 in do_handle_one_connection (thd_arg=0x3b01990) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/sql_connect.cc:1500
#20 0x00000000006f75d7 in handle_one_connection (arg=0x3b01990) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/sql/sql_connect.cc:1415
#21 0x000000000099f06e in pfs_spawn_thread (arg=0x3ae5120) at /home/laurynas/percona/src/merge-5.5.34/Percona-Server/storage/perfschema/pfs.cc:1015
#22 0x00007fe3ee193f8e in start_thread (arg=0x7fe3e2046700) at pthread_create.c:311
#23 0x00007fe3ed478e1d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:113

This was caused by an incorrect lp:~akopytov/percona-server/ahi-fixes-5.5 merge to trunk (the original branch was correct, it was the merge necessitated by the GCA and trunk tip differences):

=== modified file 'Percona-Server/storage/innobase/handler/ha_innodb.cc'
--- Percona-Server/storage/innobase/handler/ha_innodb.cc 2013-08-23 07:35:34 +0000
+++ Percona-Server/storage/innobase/handler/ha_innodb.cc 2013-09-06 13:24:59 +0000
@@ -1123,9 +1123,8 @@

        trx = thd_to_trx(thd);

- if (trx != NULL) {
- trx_search_latch_release_if_reserved(trx);
- }
+ /* No-op in XtraDB */
+ trx_search_latch_release_if_reserved(trx);

        return(0);
 }