Player leaving during spawn protection throws error

From CFC Bot:
Error
`Tried to use a NULL entity!`
Source File
`addons/cfc_spawn_protection/lua/autorun/server/sv_spawn_protection.lua:93`

This line is a `ply:ChatPrint("...")`

I believe that this is simply caused by a player leaving while in spawn protection.

Easy fix.

Start in addons/cfc_spawn_protection/lua/autorun/server/sv_spawn_protection.lua at line 93, where the ply:ChatPrint call is reported. Check the behavior when a player leaves during spawn protection and verify that the error no longer occurs. Done means the NULL entity error is prevented in that scenario.

Written by the indexing model from the issue text.