PDF工具 - 展开后，点击清空数据会崩溃

PDF Office/Views/HomePanel/PDFTools/PDFToolsContent.xaml.cs

@@ -633,6 +633,7 @@ namespace PDF_Office.Views.HomePanel.PDFTools
 
         private void ListBoxCutsWidthChanged(ListBoxEx list)
         {
+            if (list == null) return;
             //3x + 4y = containerWidth;
             //3x = y;
             //x为间距，y为item；