set default nickname empty

plugins/Common.php

@@ -131,7 +131,7 @@ Class Common {
         $dirPath = str_replace($username, $dir, $rootDir);
         $filepath = "{$dirPath}/README_nickname.txt";
 
-        $nickname = $username;
+        $nickname = '';
         if (file_exists($filepath)) {
             $nickname = file_get_contents($filepath);
             if (!empty($nickname)) {