Editing page that would normally produce a email notification causes MediaWiki error
Environment: Production
URL: https://spyro.gamepedia.com/User_talk:MarkusRost
Description: Possibly related to !91 (merged) and #131 (closed).
Originally reported in here by Pangaearocks. Later reproduced by me on Spyro.
MW Error:
[65dae557a86ea5340f62ca8f] /index.php?title=User_talk:MarkusRost&action=submit Error from line 312 of /home/hydra/public_html/includes/mail/UserMailer.php: Call to a member function toString() on string
Backtrace:
#0 /home/hydra/public_html/includes/mail/UserMailer.php(189): UserMailer::sendInternal(array, MailAddress, string, array, array)
#1 /home/hydra/public_html/includes/user/User.php(4657): UserMailer::send(array, MailAddress, string, array, array)
#2 /home/hydra/public_html/extensions/Reverb/includes/notification/NotificationEmail.php(97): User->sendMail(string, array, NULL, string)
#3 /home/hydra/public_html/extensions/Reverb/includes/notification/NotificationBroadcast.php(380): Reverb\Notification\NotificationEmail->send()
#4 /home/hydra/public_html/extensions/Reverb/includes/Hooks.php(138): Reverb\Notification\NotificationBroadcast->transmit()
#5 /home/hydra/public_html/includes/Hooks.php(177): Reverb\Hooks::onPageContentSaveComplete(WikiPage, User, WikitextContent, string, boolean, NULL, NULL, integer, Revision, Status, boolean, integer)
#6 /home/hydra/public_html/includes/Hooks.php(205): Hooks::callHook(string, array, array, NULL)
#7 /home/hydra/public_html/includes/page/WikiPage.php(1863): Hooks::run(string, array)
#8 [internal function]: WikiPage->{closure}(Wikimedia\Rdbms\DatabaseAurora, string)
#9 /home/hydra/public_html/includes/libs/rdbms/database/Database.php(3666): call_user_func_array(Closure, array)
#10 /home/hydra/public_html/includes/deferred/AtomicSectionUpdate.php(35): Wikimedia\Rdbms\Database->doAtomicSection(string, Closure)
#11 /home/hydra/public_html/includes/deferred/DeferredUpdates.php(259): AtomicSectionUpdate->doUpdate()
#12 /home/hydra/public_html/includes/deferred/DeferredUpdates.php(210): DeferredUpdates::runUpdate(AtomicSectionUpdate, Wikimedia\Rdbms\LBFactorySimple, string, integer)
#13 /home/hydra/public_html/includes/deferred/DeferredUpdates.php(127): DeferredUpdates::execute(array, string, integer)
#14 /home/hydra/public_html/includes/MediaWiki.php(606): DeferredUpdates::doUpdates(string, integer)
#15 /home/hydra/public_html/includes/MediaWiki.php(575): MediaWiki::preOutputCommit(RequestContext, Closure)
#16 /home/hydra/public_html/includes/MediaWiki.php(877): MediaWiki->doPreOutputCommit(Closure)
#17 /home/hydra/public_html/includes/MediaWiki.php(524): MediaWiki->main()
#18 /home/hydra/public_html/index.php(42): MediaWiki->run()
#19 {main}