プログラムで取得したブロック名が匿名ブロック名「*U0000」「*U0001」…だった場合の対処法

using System;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Runtime;

namespace AutoCADBlockNameFix
{
    public class BlockNameRetriever
    {
        [CommandMethod("GETBLOCKNAME")]
        public void GetBlockName()
        {
            Document doc = Application.DocumentManager.MdiActiveDocument;
            Database db = doc.Database;
            Editor ed = doc.Editor;

            PromptSelectionOptions options = new PromptSelectionOptions
            {
                MessageForAdding = "\nブロックを選択してください: "
            };
            
            PromptSelectionResult selectionResult = ed.GetSelection(options);
            if (selectionResult.Status != PromptStatus.OK)
            {
                ed.WriteMessage("\nブロックが選択されていません。");
                return;
            }

            using (Transaction tr = db.TransactionManager.StartTransaction())
            {
                foreach (ObjectId objectId in selectionResult.Value.GetObjectIds())
                {
                    Entity entity = tr.GetObject(objectId, OpenMode.ForRead) as Entity;
                    if (entity is BlockReference blockRef)
                    {
                        string blockName = blockRef.Name;

                        // ダイナミックブロックの場合は、元のブロック名を取得
                        if (blockRef.IsDynamicBlock)
                        {
                            BlockTableRecord btr = tr.GetObject(blockRef.DynamicBlockTableRecord, OpenMode.ForRead) as BlockTableRecord;
                            blockName = btr.Name;
                        }

                        ed.WriteMessage($"\nブロック名: {blockName}");
                    }
                }
                tr.Commit();
            }
        }
    }
}