Fixed issue with chests failing to save to a schematic due to a NullPointerException.

src/com/sk89q/worldedit/blocks/ChestBlock.java

@@ -105,6 +105,7 @@ public class ChestBlock extends BaseBlock implements TileEntityBlock {
         List<Tag> itemsList = new ArrayList<Tag>();
         for (int i = 0; i < items.length; i++) {
             BaseItemStack item = items[i];
+            if (item != null) {
                 Map<String,Tag> data = new HashMap<String,Tag>();
                 CompoundTag itemTag = new CompoundTag("Items", data);
                 data.put("id", new ShortTag("id", item.getID()));
@@ -113,6 +114,7 @@ public class ChestBlock extends BaseBlock implements TileEntityBlock {
                 data.put("Slot", new ByteTag("Slot", (byte)i));
                 itemsList.add(itemTag);
             }
+        }
         Map<String,Tag> values = new HashMap<String,Tag>();
         values.put("Items", new ListTag("Items", CompoundTag.class, itemsList));
         return values;