Crash On Skill_dance_switch

#0  skill_dance_switch (unit=0xb71b0c64, flag=1) at skill.c:6112
        group = (struct skill_unit_group *) 0x0
        backup = {src_id = 0, party_id = 0, guild_id = 0, map = 0,
  target_flag = 2031616, bl_flag = 9, tick = 0, limit = 0, interval = -1,
  skill_id = 321, skill_lv = 10, val1 = 0, val2 = 0, val3 = 0, valstr = 0x0,
  unit_id = 169, group_id = 0, unit_count = 0, alive_count = 0, unit = 0x0,
  state = {ammo_consume = 0, magic_power = 0, song_dance = 0}}
#1  0x080d6f42 in skill_unit_timer_sub (bl=0xb71b0c64,
    ap=0xbfafc808 "20&\v\fÃŒ|") at skill.c:9565
        unit = (struct skill_unit *) 0xb71b0c64
        group = (struct skill_unit_group *) 0xacf9f960
        tick = 202057232
        dissonance = 1 '�1'
#2  0x0804e5e3 in map_foreachobject (func=0x80d6ea0 <skill_unit_timer_sub>,
    type=32) at map.c:1259
        i = 329
        blockcount = 0
        ap = 0xbfafc808 "20&\v\fÃŒ|"
#3  0x080d6ab6 in skill_unit_timer (tid=7, tick=202057232, id=0, data=0)
    at skill.c:9701
No locals.
#4  0x0814396a in do_timer (tick=202057237) at timer.c:394
        nextmin = -5
        i = 7
        __FUNCTION__ = "do_timer"
#5  0x081411de in main (argc=1, argv=0xbfafc904) at core.c:253
        next = <value optimized out>