Fixing PHP warning/notices

main/document/document.php

@@ -42,6 +42,8 @@ $lib_path = api_get_path(LIBRARY_PATH);
 
 api_protect_course_script(true);
 
+$to_user_id = api_get_user_id();
+
 //erase temp nanogons' audio, image edit
 if (isset($_SESSION['temp_audio_nanogong']) && !empty($_SESSION['temp_audio_nanogong'])) {
     unlink($_SESSION['temp_audio_nanogong']);

main/inc/lib/document.lib.php

@@ -680,8 +680,12 @@ class DocumentManager
                     }
                     $document_folders[$row['id']] = $row['path'];
                 }
+
                 //sort($document_folders);
-                natsort($document_folders);
+
+                if (!empty($document_folders)) {
+                    natsort($document_folders);
+                }
 
                 //return results
                 return $document_folders;