Fixed a couple of bugs discovered by FindBugs.

ProtocolLib/src/main/java/com/comphenix/protocol/events/PacketContainer.java

@@ -96,6 +96,9 @@ public class PacketContainer implements Serializable {
 			andThen(new Function<BuilderParameters, Cloner>() {
 						@Override
 						public Cloner apply(@Nullable BuilderParameters param) {
+							if (param == null)
+								throw new IllegalArgumentException("Cannot be NULL.");
+							
 							return new FieldCloner(param.getAggregateCloner(), param.getInstanceProvider()) {{
 								// Use a default writer with no concept of cloning
 								writer = new ObjectWriter();

ProtocolLib/src/main/java/com/comphenix/protocol/injector/player/NetworkObjectInjector.java

@@ -54,7 +54,7 @@ public class NetworkObjectInjector extends PlayerInjector {
 	private ClassLoader classLoader;
 
 	// Shared callback filter - avoid creating a new class every time
-	private static CallbackFilter callbackFilter;
+	private volatile static CallbackFilter callbackFilter;
 	
 	// Temporary player factory
 	private static volatile TemporaryPlayerFactory tempPlayerFactory;

ProtocolLib/src/main/java/com/comphenix/protocol/injector/spigot/SpigotPacketInjector.java

@@ -349,7 +349,7 @@ public class SpigotPacketInjector implements SpigotPacketListener {
 	public Object packetQueued(Object networkManager, Object connection, Object packet) {
 		Integer id = invoker.getPacketID(packet);
 		
-		if (id != null & queuedFilters.contains(id)) {
+		if (id != null && queuedFilters.contains(id)) {
 			// Check for ignored packets
 			if (ignoredPackets.remove(packet)) {
 				return packet;