(fixed) Size 2 monster bugs always strike back twice

[Joramun]

In CSB, playing : again with worms !!

LUA ERROR: Lua Function sys_ai_near: base/monster_ai.lua:1877: dsb_reposition: Invalid size2 subtile 2
LUA ERROR: Lua Function worm2y.msg_handler[100101]: base/monster_ai.lua:1906: Invalid slave tile (inst 3601 pos 2 dir 2)

PROGRAM CRASH!
Location: 4 27 20
Reason: Invalid slave pointer to pointerize
Stack Dump:
DSBmain
DSBgameloop
run_timers
run_timers
run_timers
deliver_msg->worm2y
lua.dsb_set_facedir
pointerize
pointerize_slave

In DM, COMPILATION crash :
(I obtain the same crash with another dungeon, also obtained with RTSB)

Parsing base/objects.lua
OBJ: 397 system archs
Parsing G:\Download\Jeux\DM\DSB\DSBtest24a\dm/objects.lua
OBJ: 397 total archs
Parsing G:\Download\Jeux\DM\DSB\DSBtest24a\dm/dungeon.lua
PROGRAM CRASH!
Location: -5 0 0
Reason: Invalid slave pointer to pointerize
Stack Dump:
DSBmain