Skip an empty list of templates being deployed

See https://www.woltlab.com/community/thread/314496/

Author: dtdesign

wcfsetup/install/files/lib/system/package/ACPTemplatesFileHandler.class.php

@@ -84,6 +84,10 @@ public function checkFiles(array $files)
      */
     public function logFiles(array $files)
     {
+        if ($files === []) {
+            return;
+        }
+
         // remove file extension
         $files = \array_map(static function (string $file) {
             if (\basename($file) !== $file) {