Enable simple format in Grouping::parse()

library/Solarium/QueryType/Select/ResponseParser/Component/Grouping.php

@@ -81,6 +81,12 @@ class Grouping implements ComponentParserInterface
 
             $matches = (isset($result['matches'])) ? $result['matches'] : null;
             $groupCount = (isset($result['ngroups'])) ? $result['ngroups'] : null;
+            if ($grouping->getFormat() === GroupingComponent::FORMAT_SIMPLE) {
+                $valueGroups = [$this->extractValueGroup($valueResultClass, $documentClass, $result, $query)];
+                $groups[$field] = new FieldGroup($matches, $groupCount, $valueGroups);
+                continue;
+            }
+
             $valueGroups = array();
             foreach ($result['groups'] as $valueGroupResult) {
                 $valueGroups[] = $this->extractValueGroup($valueResultClass, $documentClass, $valueGroupResult, $query);