Fix bug in VelocityRegisteredServer#ping()

proxy/src/main/java/com/velocitypowered/proxy/server/VelocityRegisteredServer.java

@@ -124,9 +124,10 @@ public class VelocityRegisteredServer implements RegisteredServer, ForwardingAud
     }).connect(serverInfo.getAddress()).addListener((ChannelFutureListener) future -> {
       if (future.isSuccess()) {
         MinecraftConnection conn = future.channel().pipeline().get(MinecraftConnection.class);
-        conn.setActiveSessionHandler(StateRegistry.HANDSHAKE,
-            new PingSessionHandler(pingFuture, VelocityRegisteredServer.this, conn,
-                pingOptions.getProtocolVersion()));
+        PingSessionHandler handler = new PingSessionHandler(pingFuture,
+            VelocityRegisteredServer.this, conn, pingOptions.getProtocolVersion());
+        conn.setActiveSessionHandler(StateRegistry.HANDSHAKE, handler);
+        conn.addSessionHandler(StateRegistry.LOGIN, handler);
       } else {
         pingFuture.completeExceptionally(future.cause());
       }