Same/similar issue here. After updating to 2.1.0, I ran update.php and cleared the caches, but still get this error when loading any page that uses this module. Other pages (tables) are working OK...
TypeError: Drupal\views_aggregator\Plugin\views\style\Table::getCellRaw(): Return value must be of type string, false returned in Drupal\views_aggregator\Plugin\views\style\Table->getCellRaw() (line 754 of /var/www/drupal/web/modules/contrib/views_aggregator/src/Plugin/views/style/Table.php).
Same/similar issue here. After updating to 2.1.0, I ran update.php and cleared the caches, but still get this error when loading any page that uses this module. Other pages (tables) are working OK...
TypeError: Drupal\views_aggregator\Plugin\views\style\Table::getCellRaw(): Return value must be of type string, false returned in Drupal\views_aggregator\Plugin\views\style\Table->getCellRaw() (line 754 of /var/www/drupal/web/modules/contrib/views_aggregator/src/Plugin/views/style/Table.php).
Having had exactly this problem, I was grateful for the advice in #2 and #3. Thank you both!
With that help, I was able to find web/modules/contrib/csv_serialization/csv_serialization.services.yml and make the necessary changes.
That said, perhaps a note on the project page recommending users edit the yaml file and clear their cache BEFORE upgrading would heve been even more useful ;-)
Updating directly from 10.0.6 to 10.0.8 causes no issues so I'm happy this is resolved, whatever the reason. Thanks!
poker.ca → created an issue.