Handle more NOTICE messages.

[kalaspuffar]

Describe the bug
Notice: Undefined index: err in /customers/c/1/7//httpd.www//wp-content/plugins/sqrl-login/sqrl-login.php on line 655 Notice: Undefined index: err in /customers/c/1/7//httpd.www//wp-content/plugins/sqrl-login/sqrl-login.php on line 658 Warning: Cannot modify header information - headers already sent by (output started at /customers/c/1/7//httpd.www//wp-content/plugins/sqrl-login/sqrl-login.php:655) in /customers/c/1/7//httpd.www//wp-includes/pluggable.php on line 932 Warning: Cannot modify header information - headers already sent by (output started at /customers/c/1/7//httpd.www//wp-content/plugins/sqrl-login/sqrl-login.php:655) in /customers/c/1/7//httpd.www//wp-includes/pluggable.php on line 933 Warning: Cannot modify header information - headers already sent by (output started at /customers/c/1/7//httpd.www//wp-content/plugins/sqrl-login/sqrl-login.php:655) in /customers/c/1/7//httpd.www//wp-includes/pluggable.php on line 934 Notice: Undefined variable: wp_users in /customers/c/1/7//httpd.www//wp-content/plugins/sqrl-login/sqrl-login.php on line 676 Warning: Cannot modify header information - headers already sent by (output started at /customers/c/1/7//httpd.www//wp-content/plugins/sqrl-login/sqrl-login.php:655) in /customers/c/1/7//httpd.www//wp-includes/pluggable.php on line 1265 Warning: Cannot modify header information - headers already sent by (output started at /customers/c/1/7//httpd.www//wp-content/plugins/sqrl-login/sqrl-login.php:655) in /customers/c/1/7//httpd.www//wp-includes/pluggable.php on line 1268

Handle more NOTICE messages.