[youtube] Fix uploader extraction in flat playlist mode (#28045)

youtube_dl/extractor/youtube.py

@@ -308,7 +308,9 @@ class YoutubeBaseInfoExtractor(InfoExtractor):
             r'^([\d,]+)', re.sub(r'\s', '', view_count_text),
             'view count', default=None))
         uploader = try_get(
-            renderer, lambda x: x['ownerText']['runs'][0]['text'], compat_str)
+            renderer,
+            (lambda x: x['ownerText']['runs'][0]['text'],
+             lambda x: x['shortBylineText']['runs'][0]['text']), compat_str)
         return {
             '_type': 'url_transparent',
             'ie_key': YoutubeIE.ie_key(),