ComPDFKit.Tool(win) - 优化if判断逻辑

Demo/Examples/ComPDFKit.Tool/CPDFViewerTool.Command.cs

@@ -575,11 +575,11 @@ namespace ComPDFKit.Tool
                     RemoveImageBlock();
                 }
 
-                //After removing the data, you need to get the data again.
-                PDFViewer.UpdateRenderFrame();
                 if (PDFViewer != null && PDFViewer.UndoManager != null)
                 {
                     PDFViewer.UndoManager.AddHistory(groupHistory);
+                    //After removing the data, you need to get the data again.
+                    PDFViewer.UpdateRenderFrame();
                 }
             }
             else