Not display data in rows.

I'am use versión from github.com, branch 8.x-5.x with php 7.1 and php-fpm.
I created one views for display the data for one index in elasticsearch, the view get data from elasticsearch and display rows but not show any data and throw this warning:

Warning: implode(): Invalid arguments passed en Drupal\elasticsearch_connector_views\Plugin\views\query\ElasticsearchViewsQuery->execute() (línea 448 de /var/app/active/modules/contrib/elasticsearch_connector/modules/elasticsearch_connector_views/src/Plugin/views/query/ElasticsearchViewsQuery.php

This error is caused for code:

$result_doc[$field_name] = implode(' | ', $field_value);

in file modules/elasticsearch_connector_views/src/Plugin/views/query/ElasticsearchViewsQuery.php line 448.

I Am not understand why use $field_value as array, in my case alway elasticsearch send string. The type of $field_value is defined by elasticsearch?