Elasticsearch results when using PHP 7.4.7 gives "Trying to access array offset on value of type int"

Getting this on search results page when using PHP 7.4.7:

Notice: Trying to access array offset on value of type int in Drupal\elasticsearch_connector\ElasticSearch\Parameters\Builder\SearchBuilder->Drupal\elasticsearch_connector\ElasticSearch\Parameters\Builder\{closure}() (line 304 of modules/contrib/elasticsearch_connector/src/ElasticSearch/Parameters/Builder/SearchBuilder.php).

Drupal\elasticsearch_connector\ElasticSearch\Parameters\Builder\SearchBuilder->Drupal\elasticsearch_connector\ElasticSearch\Parameters\Builder\{closure}(0)
array_filter(Array, Object, 2) (Line: 305)
Drupal\elasticsearch_connector\ElasticSearch\Parameters\Builder\SearchBuilder->flattenKeys(Array, Object, 'auto') (Line: 204)
Drupal\elasticsearch_connector\ElasticSearch\Parameters\Builder\SearchBuilder->getSearchQueryOptions() (Line: 74)
Drupal\elasticsearch_connector\ElasticSearch\Parameters\Builder\SearchBuilder->build() (Line: 26)
Drupal\elasticsearch_connector\ElasticSearch\Parameters\Factory\SearchFactory::search(Object) (Line: 578)
Drupal\elasticsearch_connector\Plugin\search_api\backend\SearchApiElasticsearchBackend->search(Object) (Line: 468)
Drupal\search_api\Entity\Server->search(Object) (Line: 539)
Drupal\search_api\Query\Query->execute() (Line: 575)
Drupal\search_api\Plugin\views\query\SearchApiQuery->execute(Object) (Line: 1426)
Drupal\views\ViewExecutable->execute(NULL) (Line: 1454)
Drupal\views\ViewExecutable->render() (Line: 183)
Drupal\views\Plugin\views\display\Page->execute() (Line: 1630)
Drupal\views\ViewExecutable->executeDisplay('page', Array) (Line: 77)
Drupal\views\Element\View::preRenderViewElement(Array)
call_user_func_array(Array, Array) (Line: 100)
Drupal\Core\Render\Renderer->doTrustedCallback(Array, Array, 'Render #pre_render callbacks must be methods of a class that implements \Drupal\Core\Security\TrustedCallbackInterface or be an anonymous function. The callback was %s. Support for this callback implementation is deprecated in 8.8.0 and will be removed in Drupal 9.0.0. See https://www.drupal.org/node/2966725', 'silenced_deprecation', 'Drupal\Core\Render\Element\RenderCallbackInterface') (Line: 781)
Drupal\Core\Render\Renderer->doCallback('#pre_render', Array, Array) (Line: 372)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 200)
Drupal\Core\Render\Renderer->render(Array, ) (Line: 226)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 573)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 227)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object, Object) (Line: 117)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object, Object) (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object, 'kernel.view', Object)
call_user_func(Array, Object, 'kernel.view', Object) (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch('kernel.view', Object) (Line: 156)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 68)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 708)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)