Adding security on esprint

mods/sprint/esprint.lua

@@ -40,6 +40,7 @@ minetest.register_globalstep(function(dtime)
 	--Loop through all connected players
 	for playerName,playerInfo in pairs(players) do
 		local player = minetest.get_player_by_name(playerName)
+		if not player then return end
 		local pos = player:getpos()
 		if player ~= nil then
 			-- From playerplus :