#3319: Do not forward cancelled messages or handled commands

proxy/src/main/java/net/md_5/bungee/connection/UpstreamBridge.java

@@ -190,7 +190,7 @@ public class UpstreamBridge extends PacketHandler
                 return message;
             }
         }
-        return null;
+        throw CancelSendSignal.INSTANCE;
     }
 
     @Override