Fix not being able to access consoleplayer as a dedicated server + other more consistent checks

• access consoleplayer on dedicated
• access players[0] on dedicated
• access players[n] or player from players.iterate if player.mo is nil
• access player.mo if the player is a spectator

merged

mentioned in commit 5ec44ba3

mentioned in merge request STJr/SRB2!1322 (closed)