Server crashed

[amadin]

0.4.12-dev

2015-07-24 09:36:17: ERROR[main]: UNRECOVERABLE error occurred. Stopping server. Please fix the following error:
2015-07-24 09:36:17: ERROR[main]: ...est_game/mods/inventory_plus/inventory_plus/init.lua:99: attempt to concatenate field '?' (a nil value)
2015-07-24 09:36:17: ERROR[main]: stack traceback:
2015-07-24 09:36:17: ERROR[main]: ...est_game/mods/inventory_plus/inventory_plus/init.lua:99: in function 'get_formspec'
2015-07-24 09:36:17: ERROR[main]: ...est_game/mods/inventory_plus/inventory_plus/init.lua:110: in function 'func'
2015-07-24 09:36:17: ERROR[main]: /home/user/minetest/bin/../builtin/game/misc.lua:17: in function 'update_timers'
2015-07-24 09:36:17: ERROR[main]: /home/user/minetest/bin/../builtin/game/misc.lua:49: in function '?'
2015-07-24 09:36:17: ERROR[main]: /home/user/minetest/bin/../builtin/game/register.lua:341: in function </home/user/minetest/bin/../builtin/game/register.lua:329>

In thread 7f326aeeb740:
/home/user/minetest/minetest-master/src/server.cpp:509: void Server::step(float): A fatal error occurred: ...est_game/mods/inventory_plus/inventory_plus/init.lua:99: attempt to concatenate field '?' (a nil value)
stack traceback:
...est_game/mods/inventory_plus/inventory_plus/init.lua:99: in function 'get_formspec'
...est_game/mods/inventory_plus/inventory_plus/init.lua:110: in function 'func'
/home/user/minetest/bin/../builtin/game/misc.lua:17: in function 'update_timers'
/home/user/minetest/bin/../builtin/game/misc.lua:49: in function '?'
/home/user/minetest/bin/../builtin/game/register.lua:341: in function </home/user/minetest/bin/../builtin/game/register.lua:329>
Debug stacks:
DEBUG STACK FOR THREAD 7f324ffff700:
#0 virtual void* EmergeThread::Thread()

(Leftover data: #1 MapBlock* ServerMap::loadBlock(v3s16))
(Leftover data: #2 void ServerMap::loadBlock(std::string_, v3s16, MapSector_, bool))
(Leftover data: #3 void ItemStack::deSerialize(std::istream&, IItemDefManager*))
DEBUG STACK FOR THREAD 7f32561fc700:
#0 virtual void* EmergeThread::Thread()

(Leftover data: #1 MapBlock* ServerMap::loadBlock(v3s16))
(Leftover data: #2 void ServerMap::loadBlock(std::string_, v3s16, MapSector_, bool))
(Leftover data: #3 void ItemStack::deSerialize(std::istream&, IItemDefManager*))
DEBUG STACK FOR THREAD 7f3256bfd700:
#0 virtual void* EmergeThread::Thread()

(Leftover data: #1 MapBlock* ServerMap::loadBlock(v3s16))
(Leftover data: #2 void ServerMap::loadBlock(std::string_, v3s16, MapSector_, bool))
(Leftover data: #3 void ItemStack::deSerialize(std::istream&, IItemDefManager*))
DEBUG STACK FOR THREAD 7f32575fe700:
#0 virtual void* CurlFetchThread::Thread()

DEBUG STACK FOR THREAD 7f3257fff700:
#0 virtual void* ServerThread::Thread()
#1 void Server::Receive()

(Leftover data: #2 virtual void Server::deletingPeer(con::Peer_, bool))
(Leftover data: #3 void RemoteClient::GetNextBlocks(ServerEnvironment_, EmergeManager_, float, std::vector&))
(Leftover data: #4 void ItemStack::serialize(std::ostream&) const)
(Leftover data: #5 bool getCraftingResult(Inventory_, ItemStack&, std::vector&, bool, IGameDef_))
(Leftover data: #6 void ItemStack::deSerialize(std::istream&, IItemDefManager_))
(Leftover data: #7 void ItemStack::deSerialize(std::istream&, IItemDefManager*))
DEBUG STACK FOR THREAD 7f326aeeb740:
#0 int main(int, char**)
#1 Dedicated server branch
#2 void dedicated_server_loop(Server&, bool&)
#3 void Server::step(float)

(Leftover data: #4 void Server::DenyAccess_Legacy(irr::u16, const wstring&))
(Leftover data: #5 void Server::SendAccessDenied_Legacy(irr::u16, const wstring&))