Account for use of MutableBlockVector3 in Spline Brush (#1831)

worldedit-core/src/main/java/com/fastasyncworldedit/core/command/tool/brush/SplineBrush.java

@@ -62,7 +62,7 @@ public class SplineBrush implements Brush, ResettableTool {
             final ArrayList<BlockVector3> points = new ArrayList<>();
             if (size > 0) {
                 DFSRecursiveVisitor visitor = new DFSRecursiveVisitor(mask, p -> {
-                    points.add(p);
+                    points.add(p.toImmutable());
                     return true;
                 }, (int) size, 1);
                 List<BlockVector3> directions = visitor.getDirections();

worldedit-core/src/main/java/com/fastasyncworldedit/core/function/visitor/DFSRecursiveVisitor.java

@@ -7,8 +7,8 @@ import com.sk89q.worldedit.math.BlockVector3;
 import static com.google.common.base.Preconditions.checkNotNull;
 
 /**
- * An implementation of an {@link com.sk89q.worldedit.function.visitor.BreadthFirstSearch} that uses
- * a mask to determine where a block should be visited.
+ * An implementation of an {@link DFSVisitor} that uses a mask to determine where a block should be visited. The visit is
+ * performed using a {@link com.fastasyncworldedit.core.math.MutableBlockVector3}
  */
 public class DFSRecursiveVisitor extends DFSVisitor {
 

worldedit-core/src/main/java/com/fastasyncworldedit/core/function/visitor/DFSVisitor.java

@@ -21,6 +21,9 @@ import java.util.List;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicInteger;
 
+/**
+ * Depth-first-search visitor. The visit is performed using a {@link com.fastasyncworldedit.core.math.MutableBlockVector3}
+ */
 public abstract class DFSVisitor implements Operation {
 
     private final RegionFunction function;