add default nickname for default id

plugins/Common.php

@@ -391,7 +391,7 @@ Class Common {
         $dirPath = str_replace("/{$username}", "/{$dir}", $rootDir);
         $filepath = "{$dirPath}/README_nickname.txt";
 
-        $nickname = '';
+        $nickname = $dir;       //默认昵称跟id相同
         if (file_exists($filepath)) {
             $nickname = file_get_contents($filepath);
             if (!empty($nickname)) {