Implemented qiangxue's solution as it is much simpler.

framework/helpers/BaseFileHelper.php

@@ -49,19 +49,15 @@ class BaseFileHelper
         $parts = [];
         foreach (explode($ds, $path) as $part) {
             if ($part === '..' && !empty($parts) && end($parts) !== '..') {
-                if (array_pop($parts) === ".") {
-                    $parts[] = '..';
-                }
-            } elseif (( $part === '.' || $part === '' ) && !empty($parts)) {
+                array_pop($parts);
+            } elseif ($part === '.' || $part === '' && !empty($parts)) {
                 continue;
             } else {
                 $parts[] = $part;
             }
         }
-        if (count($parts) > 1 && $parts[0] === '.') {
-            array_shift($parts);
-        }
-        return implode($ds, $parts);
+        $path = implode($ds, $parts);
+        return $path === '' ? '.' : $path;
     }
 
     /**