Crash in I_P_List_iterator on opening a heap table in mysql-55-eb

The following weird crash was produced when running the DDL RQG test:

#0 0x00000000005b2e12 in I_P_List_iterator<TABLE, TABLE_share, I_P_List_null_counter, I_P_List_no_push_back<TABLE> >::operator++ (this=0x7f189c212f40)
    at /home/philips/bzr/mysql-55-eb/sql/sql_plist.h:175
#1 0x000000000059eb86 in check_unused () at /home/philips/bzr/mysql-55-eb/sql/sql_base.cc:205
#2 0x000000000059f3f7 in table_def_unuse_table (table=0x7f1864055710) at /home/philips/bzr/mysql-55-eb/sql/sql_base.cc:468
#3 0x00000000005a18a9 in close_thread_table (thd=0x20e2550, table_ptr=0x20e25e0) at /home/philips/bzr/mysql-55-eb/sql/sql_base.cc:1550
#4 0x00000000005a0fb7 in close_open_tables (thd=0x20e2550) at /home/philips/bzr/mysql-55-eb/sql/sql_base.cc:1293
#5 0x00000000005a15e2 in close_thread_tables (thd=0x20e2550) at /home/philips/bzr/mysql-55-eb/sql/sql_base.cc:1500
#6 0x00000000005fc5cf in mysql_execute_command (thd=0x20e2550) at /home/philips/bzr/mysql-55-eb/sql/sql_parse.cc:4369
#7 0x00000000005fed7b in mysql_parse (thd=0x20e2550,
    rawbuf=0x7f1864004c70 "INSERT IGNORE INTO local_7_2 VALUES ( NULL , 'i' , LOAD_FILE('/home/philips/bzr/randgen-heap/data/earth579kb.jpg') , 2 , LOAD_FILE('/home/philips/bzr/randgen-heap/data/earth1886kb.jpg') ) , ( 6 , 'w' "..., length=683, parser_state=0x7f189c214630)
    at /home/philips/bzr/mysql-55-eb/sql/sql_parse.cc:5503
#8 0x00000000005f2cf5 in dispatch_command (command=COM_QUERY, thd=0x20e2550,
    packet=0x20e53c1 "INSERT IGNORE INTO local_7_2 VALUES ( NULL , 'i' , LOAD_FILE('/home/philips/bzr/randgen-heap/data/earth579kb.jpg') , 2 , LOAD_FILE('/home/philips/bzr/randgen-heap/data/earth1886kb.jpg') ) , ( 6 , 'w' "..., packet_length=683) at /home/philips/bzr/mysql-55-eb/sql/sql_parse.cc:1034
#9 0x00000000005f1f52 in do_command (thd=0x20e2550) at /home/philips/bzr/mysql-55-eb/sql/sql_parse.cc:771
#10 0x00000000006d7beb in do_handle_one_connection (thd_arg=0x20e2550) at /home/philips/bzr/mysql-55-eb/sql/sql_connect.cc:776
#11 0x00000000006d7832 in handle_one_connection (arg=0x20e2550) at /home/philips/bzr/mysql-55-eb/sql/sql_connect.cc:724
#12 0x00000035a7207761 in start_thread () from /lib64/libpthread.so.0
#13 0x00000035a6ee098d in clone () from /lib64/libc.so.6