Fixes GunshipPenguin#4

  It was found that in the CTF repo they fixed this issue... but we just
simply didn't apply the fix they did.

  This was fixed in their repo as issue [623](MT-CTF/capturetheflag#623)

README.md

@@ -29,3 +29,4 @@ start to be warned via chat message.
 
 - 07/22/2021 Beanzilla added the priv bypass_afk_kick which prevents being kicked for an unlimited amount of time. (Default's
 to being granted to server admin and if single player)
+- 07/22/2021 Beanzilla fixed issue #4

init.lua

@@ -7,6 +7,7 @@ to this software to the public domain worldwide. This software is
 distributed without any warranty.
 ]]
 
+-- Settings
 local MAX_INACTIVE_TIME = 300
 local CHECK_INTERVAL = 1
 local WARN_TIME = 20
@@ -27,6 +28,10 @@ minetest.register_on_leaveplayer(function(player)
 end)
 
 minetest.register_on_chat_message(function(playerName, message)
+	-- Verify that it's a player and that it is not the terminal
+	if not playerName or not minetest.get_player_by_name(playerName) then
+		return -- Abort tracking the last action
+	end
 	players[playerName]["lastAction"] = minetest.get_gametime()
 end)