Add missing nullability annotation

proxy/src/main/java/com/velocitypowered/proxy/network/packet/serverbound/ServerboundLoginPluginResponsePacket.java

@@ -42,7 +42,12 @@ public class ServerboundLoginPluginResponsePacket extends DefaultByteBufHolder i
     }
     return new ServerboundLoginPluginResponsePacket(id, success, data);
   };
-  public static final PacketWriter<ServerboundLoginPluginResponsePacket> ENCODER = PacketWriter.deprecatedEncode();
+  public static final PacketWriter<ServerboundLoginPluginResponsePacket> ENCODER =
+      (out, packet, version) -> {
+        ProtocolUtils.writeVarInt(out, packet.id);
+        out.writeBoolean(packet.success);
+        out.writeBytes(packet.content());
+      };
 
   private final int id;
   private final boolean success;
@@ -53,13 +58,6 @@ public class ServerboundLoginPluginResponsePacket extends DefaultByteBufHolder i
     this.success = success;
   }
 
-  @Override
-  public void encode(ByteBuf buf, ProtocolVersion version) {
-    ProtocolUtils.writeVarInt(buf, id);
-    buf.writeBoolean(success);
-    buf.writeBytes(content());
-  }
-
   @Override
   public boolean handle(PacketHandler handler) {
     return handler.handle(this);

proxy/src/main/java/com/velocitypowered/proxy/network/pipeline/MinecraftDecoder.java

@@ -31,6 +31,7 @@ import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInboundHandlerAdapter;
 import io.netty.handler.codec.CorruptedFrameException;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 public class MinecraftDecoder extends ChannelInboundHandlerAdapter {
 
@@ -96,7 +97,7 @@ public class MinecraftDecoder extends ChannelInboundHandlerAdapter {
     }
   }
 
-  private Packet readPacket(int packetId, ByteBuf buf) throws Exception {
+  private @Nullable Packet readPacket(int packetId, ByteBuf buf) throws Exception {
     PacketReader<? extends Packet> reader = this.registry.lookupReader(packetId, this.version);
     if (reader == null) {
       return null;