Stop writing corrupt tile entities to schematics

also make some stuff definitely immutable.

worldedit-core/src/main/java/com/sk89q/worldedit/extent/clipboard/io/FastSchematicWriter.java

@@ -159,15 +159,16 @@ public class FastSchematicWriter implements ClipboardWriter {
                 if (nbt != null) {
                     Map<String, Tag> values = nbt.getValue();
 
-                    values.remove("id"); // Remove 'id' if it exists. We want 'Id'
-
                     // Positions are kept in NBT, we don't want that.
                     values.remove("x");
                     values.remove("y");
                     values.remove("z");
-                    if (!values.containsKey("Id")) {
                     values.put("Id", new StringTag(block.getNbtId()));
-                    }
+
+                    // Remove 'id' if it exists. We want 'Id'.
+                    // Do this after we get "getNbtId" cos otherwise "getNbtId" doesn't work.
+                    // Dum.
+                    values.remove("id");
                     values.put("Pos", new IntArrayTag(new int[]{
                             pos.getX(),
                             pos.getY(),

worldedit-core/src/main/java/com/sk89q/worldedit/world/block/BaseBlock.java

@@ -49,13 +49,8 @@ import static com.google.common.base.Preconditions.checkNotNull;
  */
 public class BaseBlock implements BlockStateHolder<BaseBlock>, TileEntityBlock {
 
-    private BlockState blockState;
-    @Nullable private CompoundTag nbtData;
-
-    @Deprecated
-    public BaseBlock() {
-        this(BlockTypes.AIR.getDefaultState());
-    }
+    private final BlockState blockState;
+    @Nullable private final CompoundTag nbtData;
 
     /**
      * Construct a block with the given type and default data.
@@ -151,6 +146,9 @@ public class BaseBlock implements BlockStateHolder<BaseBlock>, TileEntityBlock {
             return "";
         }
         Tag idTag = nbtData.getValue().get("id");
+        if (idTag == null) {
+            idTag = nbtData.getValue().get("Id");
+        }
         if (idTag instanceof StringTag) {
             return ((StringTag) idTag).getValue();
         } else {
@@ -164,6 +162,11 @@ public class BaseBlock implements BlockStateHolder<BaseBlock>, TileEntityBlock {
         return this.nbtData;
     }
 
+    @Override
+    public void setNbtData(@Nullable CompoundTag nbtData) {
+        throw new UnsupportedOperationException("This class is immutable.");
+    }
+
     /**
      * Checks whether the type ID and data value are equal.
      */