[Plugin: Link Library] Cannot modify header information errors with plugin version 4.26

I’m getting various header errors, like
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 890

and when I log off I get a page with

Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-login.php on line 337
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-login.php on line 349
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 717
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 718
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 719
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 720
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 721
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 722
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 725
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 726
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 727
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 728
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 731
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 732
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 733
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 734
Warning: Cannot modify header information - headers already sent by (output started at .../public_html/wp-content/plugins/link-library/link-library.php:1) in .../public_html/wp-includes/pluggable.php on line 890