Invalid timers warning

[Nirnael]

Runtime log at: https://tgstation13.org/parsed-logs/sybil/data/logs/2019/02/11/round-101661 Formatted a bit for easier reading. Repeats at least 100 times, same exact warning.

[2019-02-11 09:10:55.769] ## WARNING: Invalid timer:
Timer: 
    Timer: -1 ([0x2100f4ad]),
    TTR: 40347, 
    Flags: ,
        callBack: [0x21078836],
        callBack.object: Evil Crab[0x3000012](/mob/living/simple_animal/crab/evil),
        callBack.delegate:/mob/living/proc/med_hud_set_status()
    Prev:
        Timer: -1 ([0x210795d3])
        TTR: 40347 
        Flags:
            TIMER_UNIQUE, 
            TIMER_OVERRIDE, 
            TIMER_NO_HASH_WAIT,
            callBack: [0x210795c6],
            callBack.object: Mining External Airlock[0x200c8bd](/obj/machinery/door/airlock/external), callBack.delegate:/obj/machinery/door/proc/autoclose(),
    Next: 
        Timer: -1 ([0x210795d3]), 
        TTR: 40347, 
        Flags: 
        TIMER_UNIQUE, 
        TIMER_OVERRIDE, 
        TIMER_NO_HASH_WAIT, 
        callBack: [0x210795c6], 
        callBack.object: Mining External Airlock[0x200c8bd](/obj/machinery/door/airlock/external), 
        callBack.delegate:/obj/machinery/door/proc/autoclose()

SPENT(39748.5)
QDELETED
NO CALLBACK
world.time: 40347.5, head_offset: 40347, practical_offset: 1 in code/controllers/subsystem/timer.dm at line 282 src: Timer usr: .

[timothymtorres]

Linking these all together since they seem possibly related or dupes:

56292

42741

54881

51164

48484

30423

[Mooshimi]

common runtime