After installation, visiting admin/setting/sparkpost results in a crash
Using CiviCRM 5.51.1 on Backdrop CMS. After installing the Sparkpost extension (version 1.5, 2022-07-25 release), attempting to visit the admin page at admin/setting/sparkpost results in a CiviCRM crash, displaying the error "Cannot decrypt token. Invalid format" on the page.
The Backdrop watchdog log shows a huge number (many pages) of PHP errors, "Notice: Array to string conversion in Civi\Core\SettingsMetadata::_filterSettingsSpecification() (line 133 of /mysite/modules/contrib/civicrm/Civi/Core/SettingsMetadata.php)."
Followed by "Notice: Undefined index: sparkpost_apiKey in CRM_Sparkpost::getSetting() (line 54 of /mysite/files/civicrm/ext/com.cividesk.email.sparkpost/CRM/Sparkpost.php)."
and then "$Fatal Error Details = array:3 [ "message" => "Cannot decrypt token. Invalid format." ", and then a backtrace.