Lua Error

I got this lua error, can anyone help?

[ERROR] A runtime error has occurred in “gamemodes/darkrp/gamemode/libraries/fn.lua” on line 80.
The best help I can give you is this:

Attempt to call Name/Nick/GetName on a non-existing player!

Hints:
- No hints, sorry.

The responsibility for this error lies with (the authors of) one (or more) of these files:
1. gamemodes/darkrp/gamemode/libraries/fn.lua on line 80
2. gamemodes/darkrp/gamemode/modules/base/sh_entityvars.lua on line 105
3. addons/enforcer/lua/autorun/server/enforcer.lua on line 561
------- End of Simplerr error -------

Maybe problems with an nextbot/playerbot or such?

probably an old version of darkrp