attempt to perform arithmetic on a nil value

gistfile1.txt

20:43:25: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:25: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:25: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:25: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:25: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:25: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:25: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:25: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:25: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:25: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:27: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:27: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:27: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:27: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:27: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:42: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:42: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:42: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:42: ERROR[ServerThread]: pathfinder: failed to update cost map
20:43:42: ERROR[ServerThread]: pathfinder: failed to update cost map
20:44:12: ERROR[ServerThread]: pathfinder: failed to update cost map
20:44:12: ERROR[ServerThread]: pathfinder: failed to update cost map
20:44:12: ERROR[ServerThread]: pathfinder: failed to update cost map
20:44:12: ERROR[ServerThread]: pathfinder: failed to update cost map
20:44:12: ERROR[ServerThread]: pathfinder: failed to update cost map
voxel-ing rail: elapsed time: 0.00ms
carts: is_rail hit ignore, trying again with get_content: now nn= carts:powerrail group rail= 1 p=(31,-5,-54)
voxel-ing rail: elapsed time: 0.00ms
carts: is_rail hit ignore, trying again with get_content: now nn= carts:powerrail group rail= 1 p=(-129,7,-152)
voxel-ing rail: elapsed time: 0.00ms
carts: is_rail hit ignore, trying again with get_content: now nn= default:rail group rail= 1 p=(-145,7,-152)
voxel-ing rail: elapsed time: 10.00ms
carts: is_rail hit ignore, trying again with get_content: now nn= carts:powerrail group rail= 1 p=(-80,5,82)
voxel-ing rail: elapsed time: 0.00ms
carts: is_rail hit ignore, trying again with get_content: now nn= carts:powerrail group rail= 1 p=(-64,5,82)
voxel-ing rail: elapsed time: 0.00ms
carts: is_rail hit ignore, trying again with get_content: now nn= carts:powerrail group rail= 1 p=(-48,5,82)
7
20:48:22: ERROR[main]: ERROR: An unhandled exception occurred: ...tekmine/var/minetest/minetest/bin/../mods/carts/init.lua:561: attempt to perform arithmetic on a nil value
20:48:22: ERROR[main]: stack traceback:
20:48:22: ERROR[main]: ...tekmine/var/minetest/minetest/bin/../mods/carts/init.lua:561: in function <...tekmine/var/minetest/minetest/bin/../mods/carts/init.lua:275>

In thread 7fa425f04800:
/home2/lotekmine/var/minetest/minetest/src/main.cpp:1945: int main(int, char**): Assertion '0' failed.
Debug stacks:
DEBUG STACK FOR THREAD 7fa425f04800:
#0 int main(int, char**)
(Leftover data: #1 Dedicated server branch)
(Leftover data: #2 virtual void ServerMap::save(ModifiedState))
(Leftover data: #3 void ItemStack::serialize(std::ostream&) const)