Critical error in wp-admin

When searching through posts of custom post types in the wp-admin screen (we have a few types), filtering by author (located by default above post table) throws the following error:

Error Message:
An error occurred while writing to the "" key
Occurred at:
/nas/content/live/kwindslive/wp-content/plugins/wp-rss-aggregator/src/Data/AbstractDataSet.php (65)
Stack trace:
#0 /nas/content/live/kwindslive/wp-content/plugins/wp-rss-aggregator/src/Handlers/FeedTemplates/CreateDefaultFeedTemplateHandler.php(54): RebelCode\Wpra\Core\Data\AbstractDataSet->offsetSet(NULL, Array)
#1 /nas/content/live/kwindslive/wp-includes/class-wp-hook.php(286): RebelCode\Wpra\Core\Handlers\FeedTemplates\CreateDefaultFeedTemplateHandler->__invoke('')
#2 /nas/content/live/kwindslive/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array)
#3 /nas/content/live/kwindslive/wp-includes/plugin.php(453): WP_Hook->do_action(Array)
#4 /nas/content/live/kwindslive/wp-settings.php(467): do_action('init')
#5 /nas/content/live/kwindslive/wp-config.php(117): require_once('/nas/content/li...')
#6 /nas/content/live/kwindslive/wp-load.php(37): require_once('/nas/content/li...')
#7 /nas/content/live/kwindslive/wp-admin/admin.php(31): require_once('/nas/content/li...')
#8 /nas/content/live/kwindslive/wp-admin/edit.php(10): require_once('/nas/content/li...')
#9 {main}

The error is not thrown when filtering standard posts or pages in this manner. Client has purchased the premium bundle and we have installed the full text and feed to post addons. I will ask him to submit a support ticket through your contact portal as well. Thanks.

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