fix 1 byte long disconnect reason (#4150)

Signed-off-by: Stefan <stefan.pingel@consensys.net>

ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/rlpx/connections/netty/DeFramer.java

@@ -205,7 +205,7 @@ final class DeFramer extends ByteToMessageDecoder {
     if (remoteAddress == null) {
       return Optional.empty();
     }
-    int port = peerInfo.getPort();
+    final int port = peerInfo.getPort();
     return Optional.of(
         DefaultPeer.fromEnodeURL(
             EnodeURLImpl.builder()

ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/rlpx/wire/messages/DisconnectMessage.java

@@ -80,9 +80,14 @@ public final class DisconnectMessage extends AbstractMessageData {
     }
 
     public static Data readFrom(final RLPInput in) {
-      in.enterList();
-      Bytes reasonData = in.readBytes();
-      in.leaveList();
+      Bytes reasonData = Bytes.EMPTY;
+      if (in.nextIsList()) {
+        in.enterList();
+        reasonData = in.readBytes();
+        in.leaveList();
+      } else if (in.nextSize() == 1) {
+        reasonData = in.readBytes();
+      }
 
       // Disconnect reason should be at most 1 byte, otherwise, just return UNKNOWN
       final DisconnectReason reason =