在WordPress中设置阻止直接访问方法后，主题不再起作用

Question

I experienced the following issues during my WordPress theme development:

1. If I set up the 'prevent direct access' method on the top of every WP PHP file, I can't reach the WP admin dashboard anymore, I see only the white screen. Anyway, the front-end works correctly. If I delete this lines in my PHP codes, it doesn't solve this problem, because I can't reach the WP admin dashboard still.

Here is the code I'm using:

<?php if ( ! defined( 'ABSPATH' ) ) exit; ?>

1. If I activate another theme and login into WP admin dashboard, after re-activating my original theme works fine further. But, If I logout again from the WP admin dashboard, I get a bad redirection with the following lines: 'wp-login.php?action=logout&_wpnonce=94d379d5aa'

Do you have any ideas, what could be the solution?

Thanks a lot!

Frank