Fix sign extension issue when encoding 2-byte number for packets. Con…

…verting short back to ushort before it gets extended to int fixes the problem.

EOLib/Net/PacketBuilder.cs

@@ -67,7 +67,7 @@ public IPacketBuilder AddChar(byte b)
 
         public IPacketBuilder AddShort(short s)
         {
-            return AddBytes(_encoderService.EncodeNumber(s, 2));
+            return AddBytes(_encoderService.EncodeNumber((ushort)s, 2));
         }
 
         public IPacketBuilder AddThree(int t)