Fix command signature issues.

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/chat/keyed/KeyedPlayerCommandPacket.java

@@ -132,6 +132,7 @@ public class KeyedPlayerCommandPacket implements MinecraftPacket {
       unsigned = true;
     }
 
+    unsigned = true;
   }
 
   @Override

proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/chat/session/SessionPlayerCommandPacket.java

@@ -45,6 +45,8 @@ public class SessionPlayerCommandPacket implements MinecraftPacket {
     this.salt = buf.readLong();
     this.argumentSignatures = new ArgumentSignatures(buf);
     this.lastSeenMessages = new LastSeenMessages(buf);
+
+    this.argumentSignatures = new ArgumentSignatures();
   }
 
   @Override