Fix crash

src/frames/mainwindow.cpp

@@ -702,6 +702,10 @@ void MainWindow::redrawTaskTree()
 {
     QTreeWidget *l = ui->taskList;
     uint16_t itemCount = l->topLevelItemCount();
+    if (itemCount == 0)
+    {
+        return;
+    }
     for (int16_t i = itemCount; i >= 0; i--)
     {
         delete l->takeTopLevelItem(i);