"Trying to remove nonexistant room build callback" freeze/crash

[FlibGibs]

What steps will reproduce the problem?

1. Run Autosave7.sav
2. Wait a few seconds
3. The game will freeze/crash

What version of CorsixTH are you using (e.g. "0.30", "4c66e39985")?

0.5 RC1

What operating system / compile settings are you using?

Windows 10

What level was this on (e.g. "Demo level", "Full game level 12")?

Level 10 (Eggsenham)

Please provide any additional information below.

Uploads of gamelog and autosaves here: https://db.tt/AgUDUY76
I've included Autosave6 as well, in case this helps shed light on what changed between the two saves to cause the crash.

gamelog.txt output

Created game with savegame version 105.
Warning: Trying to remove nonexistant room build callback (function: 0000000F2E6AFC80) from humanoid (table: 0000000F2ED67EE0).
Warning: Trying to remove nonexistant room remove callback (function: 0000000F2A485F80) from humanoid (table: 0000000F2ED67EE0).
[repeated mulitple times]
Warning: Trying to remove nonexistant room build callback (function: 0000000F2E159FE0) from humanoid (table: 0000000F23930A00).
Warning: Trying to remove nonexistant room remove callback (function: 0000000F2A343B40) from humanoid (table: 0000000F23930A00).
Error in timer handler: 
C:\Program Files\CorsixTH\Lua\entities\humanoid.lua:662: Can only finish current action
stack traceback:
    [C]: in function 'assert'
    C:\Program Files\CorsixTH\Lua\entities\humanoid.lua:662: in method 'finishAction'
    C:\Program Files\CorsixTH\Lua\rooms\general_diag.lua:75: in field 'after_use'
    ...Files\CorsixTH\Lua\humanoid_actions\multi_use_object.lua:264: in local 'timer_function'
    C:\Program Files\CorsixTH\Lua\entity.lua:218: in method 'tick'
    C:\Program Files\CorsixTH\Lua\world.lua:1121: in method 'onTick'
    C:\Program Files\CorsixTH\Lua\app.lua:878: in function <C:\Program Files\CorsixTH\Lua\app.lua:875>
    (...tail calls...)
    C:\Program Files\CorsixTH\Lua\app.lua:779: in function <C:\Program Files\CorsixTH\Lua\app.lua:774>

[Alberth289346]

Cannot reproduce this in current trunk (a54ddfa, October 2015). Did you try in 0.50 release?

[mugmuggy]

Fixed with #1567