get_current_screen() fatal error while building my theme

Hi,
I’m building a theme from scratch, and it seems that 3 or 4 times a day, something I do causes this error:

Fatal error: Call to a member function add_help_tab() on a non-object in C:\WP_Network\xampp\htdocs\wordpress\wp-admin\widgets.php on line 42

The file name changes sometimes, but this error happens when I’m trying to do things in the Admin panel.

This most recent time, it wasn’t caused by changing a file, so I’m not sure how to fix it. I was in the Appearance > Menus section. I opened the Screen Options window along the top, and I hid one of the panels, and ever since I did that, I’ve been getting this error. I forget which panel it was, but it was the default top-left panel.

Is there something I should look for, or make sure to do, not do, or add to stop these get_current_screen() fatal error triggers?

Also, is there some way I can force WordPress to reset all of my admin section settings (panels I’ve hidden) so that I can get the admin panel working again?