Set uploader default values to None

youtube_dl/extractor/xnxx.py

@@ -100,8 +100,8 @@ class XNXXIE(InfoExtractor):
         tags = self._search_regex(r'<meta name="keywords" content="porn,porn movies,free porn,free porn movies,sex,porno,free sex,tube porn,tube,videos,full porn,xxnx,xnxxx,xxx,pussy,(?P<tags>.+?)"', webpage, 'tags', group='tags', default='').split(',')
 
         uploader_data = re.findall(r'<a class=".+?-plate" href="(?P<uploader_url>.+?)">(?P<uploader_name>.+?)</a>', webpage)
-        uploader_id = ''
-        uploader_url = ''
+        uploader_id = None
+        uploader_url = None
         if uploader_data != []:
             uploader_url, uploader_id = uploader_data[0][0:2]