[youtube] apply the fix for lists with number of videos multiple of _MAX_RESULTS to user extraction

Copied from the playlist extractor.

youtube_dl/extractor/youtube.py

@@ -1005,6 +1005,9 @@ def _real_extract(self, url):
                 response = json.loads(page)
             except ValueError as err:
                 raise ExtractorError(u'Invalid JSON in API response: ' + compat_str(err))
+            if 'entry' not in response['feed']:
+                # Number of videos is a multiple of self._MAX_RESULTS
+                break
 
             # Extract video identifiers
             ids_in_page = []