Fix HashTreeSet which went missing in the previous commit.

nms-patches/WorldServer.patch

@@ -26,7 +26,7 @@
 -    private final Set<NextTickListEntry> L = Sets.newHashSet();
 -    private final TreeSet<NextTickListEntry> M = new TreeSet();
 +    // private final Set<NextTickListEntry> L = Sets.newHashSet(); // PAIL: Rename nextTickListHash
-+    private final TreeSet<NextTickListEntry> M = new TreeSet(); // CraftBukkit - HashTreeSet // PAIL: Rename nextTickList
++    private final HashTreeSet<NextTickListEntry> M = new HashTreeSet<NextTickListEntry>(); // CraftBukkit - HashTreeSet // PAIL: Rename nextTickList
      private final Map<UUID, Entity> entitiesByUUID = Maps.newHashMap();
      public ChunkProviderServer chunkProviderServer;
      public boolean savingDisabled;