Fix back button on Load from DL
This patch fixes the issue of clicking back and load from DL again without a file opened. When the page "dlteams" exists but the page "poeditor" doesn't it's not possible to call replace_with_tags with "poeditor", so we need to use the current page in the navigation_view.
In the future we can use the adw_navigation_view_get_visible_page_tag directly instead of getting the AdwNavigationPage and calling get_tag, but this function is still unstable and will be available since version 1.7.