To solve the Blank Screen while viewing "User Defined" errors in the Error Log Screen.
In the .htaccess file find the following line:
'RewriteCond %{QUERY_STRING} ^.*(else|case|switch|defined|require|include|function|return|isset|foreach|global).* [NC]' . PHP_EOL .
and change it to
'RewriteCond %{QUERY_STRING} ^.*(else|case|switch|require|include|function|isset|foreach|global).* [NC]' . PHP_EOL .
We are removing the keyword "defined".