Fix TablistManager add Team visibility

src/de/steamwar/bungeecore/listeners/TablistManager.java

@@ -241,7 +241,8 @@ public class TablistManager extends BasicListener {
         }
 
         private Team getTeam(ProxiedPlayer p) {
-            return Team.get(SteamwarUser.get(p).getTeam());
+            Team team = Team.get(SteamwarUser.get(p).getTeam());
+            return team.getTeamId() <= 0 ? null : team;
         }
 
         private String getTablistName(ProxiedPlayer p, boolean sameServer) {