Fix PacketContainer serialization (#2479)

Fixes #2478

Author: Mr-EmPee

src/main/java/com/comphenix/protocol/PacketType.java

@@ -731,7 +731,7 @@ public String getMojangName() {
     private boolean forceAsync;
 
     private boolean dynamic;
-    private int hashCode;
+    private transient int hashCode;
 
     /**
      * Retrieve the current packet/legacy lookup.