Handle empty packets too

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftVarintFrameDecoder.java

@@ -33,8 +33,10 @@ public class MinecraftVarintFrameDecoder extends ByteToMessageDecoder {
       if (reader.result == DecodeResult.SUCCESS) {
         if (reader.readVarint < 0) {
           throw BAD_LENGTH_CACHED;
-        }
+        } else if (reader.readVarint == 0) {
-
+          // skip over the empty packet and ignore it
+          in.readerIndex(varintEnd + 1);
+        } else {
           int minimumRead = reader.bytesRead + reader.readVarint;
           if (in.isReadable(minimumRead)) {
             out.add(in.retainedSlice(varintEnd + 1, reader.readVarint));
@@ -42,6 +44,7 @@ public class MinecraftVarintFrameDecoder extends ByteToMessageDecoder {
           } else {
             return;
           }
+        }
       } else if (reader.result == DecodeResult.TOO_BIG) {
         throw VARINT_BIG_CACHED;
       } else if (reader.result == DecodeResult.TOO_SHORT) {