Fix Varint21FrameDecoder cached length buf usage

patches/server/Optimize-NetworkManager-Exception-Handling.patch

@@ -34,13 +34,14 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +        }
 +        // Paper end
          byteBuf.markReaderIndex();
+-        byte[] bs = new byte[3];
 +        // Paper start - reuse temporary length buffer
-+        byte[] abyte = lenBuf;
-+        java.util.Arrays.fill(abyte, (byte) 0);
++        byte[] bs = lenBuf;
++        java.util.Arrays.fill(bs, (byte) 0);
 +        // Paper end
-         byte[] bs = new byte[3];
  
          for(int i = 0; i < bs.length; ++i) {
+             if (!byteBuf.isReadable()) {
 diff --git a/src/main/java/net/minecraft/network/protocol/PacketUtils.java b/src/main/java/net/minecraft/network/protocol/PacketUtils.java
 index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
 --- a/src/main/java/net/minecraft/network/protocol/PacketUtils.java