Error on WP version 5.0.3

Hi,

after editing/updating an existing locker I get the following error in a white page:

Notice: Undefined index: opanda_fields in /home/bamboosc/scubarob.love/wp-content/plugins/opt-in-panda/panda-items/email-locker/admin/metaboxes/subscription-options.php on line 908

Warning: Cannot modify header information – headers already sent by (output started at /home/bamboosc/scubarob.love/wp-content/plugins/opt-in-panda/panda-items/email-locker/admin/metaboxes/subscription-options.php:908) in /home/bamboosc/scubarob.love/wp-includes/pluggable.php on line 1223

However, the locker updates correctly and is correctly shown on the live website; it also allows for registration.

Thanks,

S