Merge pull request #76 from Roxayl/bugfix/null-category-returned

Return early if no nested categories retrieved

ps_categorytree.php

@@ -139,6 +139,9 @@ private function getCategories($category): array
 
         // Retrieve them using the built in method
         $categories = Category::getNestedCategories($category->id, $this->context->language->id, true, $groups, true, $sqlFilter, $orderBy);
+        if (empty($categories)) {
+            return [];
+        }
 
         // Get path to current category so we can use it for marking
         $idsOfCategoriesInPath = $this->getIdsOfCategoriesInPathToCurrentCategory();