Welcome panel does not check theme support for current theme

[MikeHansenMe]

On the dashboard when the welcome screen shows. It shows "Manage widgets or menus." If the theme does not support widgets the widget link goes to an error page that shows "The theme you are currently using isn’t widget-aware...". If the theme does not support menus the menu link will still take you to the nav-menus.php page(which does not show in the nav) but it is fairly useless. If you click "Add new menu" it send you to an error page. I think it would be best to stop users before they get to an error or page to confuse them more.

Related #25949

[MikeHansenMe]

check for theme support

[MikeHansenMe]

So the menu link just takes you to a error page as well. I had added a menu while testing that allowed me to access the page.

[obenland]

Nice catch Mike

[nacin]

In 27563:

Cap and theme support checks for the welcome panel.

props MikeHansenMe.
fixes #26276.