fix a typo

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

@@ -46,6 +46,7 @@ public class MinecraftVarintFrameDecoder extends ByteToMessageDecoder {
     // skip any runs of 0x00 we might find
     int packetStart = in.forEachByte(FIND_NON_NUL);
     if (packetStart == -1) {
+      in.clear();
       return;
     }
     in.readerIndex(packetStart);