The following error was getting generated in the error log of wp-admin and the wp-admin was loading a white screen.

PHP Fatal error: Access to undeclared static property: WP_Screen::$this in /home/bunny/public_html/wp-admin/includes/screen.php on line 706

Fix

Open file blog/wp-admin/includes/screen.php in a text editor.
On line 706 find the following PHP statement: _help_sidebar; ?>
Replace it with the statement: _help_sidebar; ?>

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