Server: Validate _sp_sv_info_map_next cvar on map end

[Acadie]

Validate _sp_sv_info_map_next cvar on map end
Author: Acadie
Description: When the map ends, make sure the _sp_sv_info_map_next doesn't hold an erroneous map name value in which it will prevent the server from not loading its next map. An erroneous value is a result of the map command being issued when the server doesn't have the map.
Setup: Put this to ./sofplus/addons