Minor - format code.

main/group/group_creation.php

@@ -123,6 +123,7 @@ if (isset($_POST['number_of_groups'])) {
 		}
 		$group_categories = GroupManager::get_categories();
 		$group_id = GroupManager :: get_number_of_groups() + 1;
+		$cat_options = [];
 		foreach ($group_categories as $index => $category) {
 			$cat_options[$category['id']] = $category['title'];
 		}