Fixed bug with weapons not costing anything server-side

core/src/io/anuke/mindustry/net/Packets.java

@@ -114,4 +114,8 @@ public class Packets {
     public enum KickReason{
         kick, invalidPassword
     }
+
+    public static class UpgradePacket{
+        public int id; //weapon ID only, currently
+    }
 }

core/src/io/anuke/mindustry/net/Registrator.java

@@ -34,6 +34,7 @@ public class Registrator {
                 DisconnectPacket.class,
                 ChatPacket.class,
                 KickPacket.class,
+                UpgradePacket.class,
 
                 Class.class,
                 byte[].class,