Fallback to "default" and check if directory exists

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

config/config.sample.php

@@ -244,7 +244,7 @@ $CONFIG = array(
  * skeleton files.
  * ``{lang}`` can be used as a placeholder for the language of the user.
  * If the directory does not exist, it falls back to non dialect (from ``de_DE``
- * to ``de``). If that does not exist either, it falls back to ``en``
+ * to ``de``). If that does not exist either, it falls back to ``default``
  *
  * Defaults to ``core/skeleton`` in the Nextcloud directory.
  */
@@ -866,6 +866,7 @@ $CONFIG = array(
 /**
  * custom path for LibreOffice/OpenOffice binary
  *
+ *
  * Defaults to ``''`` (empty string)
  */
 'preview_libreoffice_path' => '/usr/bin/libreoffice',

lib/private/legacy/util.php

@@ -389,7 +389,10 @@ class OC_Util {
 				$skeletonDirectory = str_replace('{lang}', substr($userLang, 0, $dialectStart), $plainSkeletonDirectory);
 			}
 			if ($dialectStart === false || !file_exists($skeletonDirectory)) {
-				$skeletonDirectory = str_replace('{lang}', 'en', $plainSkeletonDirectory);
+				$skeletonDirectory = str_replace('{lang}', 'default', $plainSkeletonDirectory);
+			}
+			if (!file_exists($skeletonDirectory)) {
+				$skeletonDirectory = '';
 			}
 		}