It is safe to just dismiss that notice as it could be a one-time event due to updates and all should be fine with WPML after you close that notice. We had a similar issue before but it was handled already in the current version.
❌ Before doing that please backup your database and website for safety. ❌
In the case where you can’t dismiss this notice, you can solve it by removing the empty value from your database table "wp_icl_strings" using database tools like PHPMyAdmin (or similar) or you can simply remove the entry from inside WPML > String Translation.
Please let me know if this solved your issue or if you still need help.