FPC related PHP warning (might block) when deleting an Optimizer with search terms limitations

[rbayet]

Preconditions

Magento Version : EE 2.3.0, 2.3.2

ElasticSuite Version : 2.8.2 and 2.8.x

Environment : Developer

Third party modules : N/A

Steps to reproduce

1. Make sure to enable the default FPC in admin
2. Create an optimizer applicable on the catalog product search container and with search query terms limitations
3. From the optimizers grid, try to delete the optimizer

Expected result

1. The optimizer should be deleted, with a success notice being displayed

Actual result

1. The browser redirects to the optimizer edit screen and an error notice is display with the error message "Warning: Illegal string offset 'id' in /var/www/ee232/vendor/smile/elasticsuite/src/module-elasticsuite-catalog-optimizer/Model/Optimizer/Limitation/Identities.php on line 115"

The issue seems to be that the Identities class expects $data['quick_search_container']['query_ids'] to be an array of dynamic rows as in \Smile\ElasticsuiteCatalogOptimizer\Model\Optimizer\Limitation\SaveHandler::getQueryIdsLimitation but this is not consistent when simply deleting the optimizer from the grid.

Additionally, Identities is not consistent either with the side effects the ReadHandler perform in \Smile\ElasticsuiteCatalogOptimizer\Model\Optimizer\Limitation\ReadHandler::getSearchQueryLimitation so I'm a bit lost there.

Anyway, if there are cases (from the edit form ?) where $data['quick_search_container']['query_ids'] is indeed an array of array, a check should be added in the loop to extract the query id either from $query or $query['id'] :

        if (!empty($data['quick_search_container']['query_ids'])) {
            foreach ($data['quick_search_container']['query_ids'] as $query) {
                $queryIds[] = $query['id'];
            }
        }