Fixed issue #537. Valentina crashes when use undo command.

--HG--
branch : feature

src/app/valentina/mainwindow.cpp

@@ -2261,6 +2261,7 @@ void MainWindow::Clear()
     qt_ntfs_permission_lookup--; // turn it off again
 #endif /*Q_OS_WIN32*/
     qApp->getUndoStack()->clear();
+    toolOptions->ClearPropertyBrowser();
     toolOptions->itemClicked(nullptr);
 }