Fix tablist header and footer desync (#1103)

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/TransitionSessionHandler.java

@@ -91,10 +91,9 @@ public class TransitionSessionHandler implements MinecraftSessionHandler {
   @Override
   public boolean handle(JoinGame packet) {
     MinecraftConnection smc = serverConn.ensureConnected();
-    RegisteredServer previousServer = serverConn.getPreviousServer().orElse(null);
+    final RegisteredServer previousServer = serverConn.getPreviousServer().orElse(null);
-    VelocityServerConnection existingConnection = serverConn.getPlayer().getConnectedServer();
-
     final ConnectedPlayer player = serverConn.getPlayer();
+    final VelocityServerConnection existingConnection = player.getConnectedServer();
 
     if (existingConnection != null) {
       // Shut down the existing server connection.
@@ -103,10 +102,10 @@ public class TransitionSessionHandler implements MinecraftSessionHandler {
 
       // Send keep alive to try to avoid timeouts
       player.sendKeepAlive();
+    }
 
     // Reset Tablist header and footer to prevent desync
     player.clearPlayerListHeaderAndFooter();
-    }
 
     // The goods are in hand! We got JoinGame. Let's transition completely to the new state.
     smc.setAutoReading(false);