Apply utf8_encode only on unrecognized encoded string

inc/poche/Tools.class.php

@@ -247,9 +247,16 @@ final class Tools
             }
         }
         else if (is_string ($data))
+        {
+            if ('' == mb_detect_encoding($data))
             {
                 return utf8_encode($data);
             }
+            else
+            {
+                return $data;
+            }
+        }
         return $data;
     }