firewall option fixed in host a game

src/netmenu.c

@@ -202,6 +202,12 @@ multiplayer_firstrun ()
 void
 host_multiplayer_game ()
 {
+	
+	if (bman.firewall) {
+		menu_displaymessage ("Firewall Option", "You can't start a game with Firewall enabled.");
+		return;
+	}
+	
     multiplayer_firstrun ();
 
     while (bman.state != GS_startup && bman.state != GS_quit) {