Impossible to create random dungeon game

[KroArtem]

As it's stated in the title, when I try to create custom game with random dungeon map, the game exits with the following information in terminal:

[string "scripts/map_generation.lua"]:5522: bad argument #1 to 'insert' (table expected, got nil)
stack traceback:
    [C]: in function 'insert'
    [string "scripts/map_generation.lua"]:5522: in function 'GenerateRandomDungeon'
    [string "./maps/random/random-map-dungeon.sms"]:3: in main chunk
    [C]: in function 'StartMap'
    [string "scripts/guichan.lua"]:779: in function 'RunMap'
    [string "scripts/guichan.lua"]:1104: in function 'callback'
    [string "scripts/guichan.lua"]:160: in function <[string "scripts/guichan.lua"]:158>
    [C]: in function 'run'
    [string "scripts/guichan.lua"]:1365: in function 'RunSinglePlayerCustomGameMenu'
    [string "scripts/guichan.lua"]:942: in function 'callback'
    [string "scripts/guichan.lua"]:160: in function <[string "scripts/guichan.lua"]:158>
    [C]: in function 'run'
    [string "scripts/guichan.lua"]:957: in function 'RunSinglePlayerGameMenu'
    [string "scripts/guichan.lua"]:1390: in function 'callback'
    [string "scripts/guichan.lua"]:160: in function <[string "scripts/guichan.lua"]:158>
    [C]: in function 'run'
    [string "scripts/guichan.lua"]:1412: in function 'BuildProgramStartMenu'
    [string "scripts/guichan.lua"]:1424: in function 'RunProgramStartMenu'
    [string "scripts/guichan.lua"]:1479: in main chunk
[Thread 0x7fffea62c700 (LWP 11056) exited]
[Thread 0x7fffefbd4700 (LWP 11054) exited]
[Thread 0x7fffec169700 (LWP 11057) exited]
[Inferior 1 (process 11053) exited with code 01]

[Andrettin]

Thank you, I've fixed it now :)

https://github.com/Andrettin/Wyrmsun/commit/ddb067d3b662d37ad39700364a1a49a0219a571c