Correctly unregister player on quit and close clipboard if using disk.

worldedit-bukkit/src/main/java/com/sk89q/worldedit/bukkit/BukkitPlayer.java

@@ -392,6 +392,7 @@ public class BukkitPlayer extends AbstractPlayerActor {
     @Override
     public void unregister() {
         player.removeMetadata("WE", WorldEditPlugin.getInstance());
+        super.unregister();
     }
 
 }

worldedit-core/src/main/java/com/sk89q/worldedit/entity/Player.java

@@ -370,9 +370,10 @@ public interface Player extends Entity, Actor {
     default void unregister() {
         cancel(true);
         if (Settings.IMP.HISTORY.DELETE_ON_LOGOUT) {
-            getSession().setClipboard(null);
             getSession().clearHistory();
             getSession().unregisterTools(this);
+        } else if (Settings.IMP.CLIPBOARD.USE_DISK) {
+            getSession().setClipboard(null);
         }
     }