Fix bug in writing playlist info-json

Closes #4889

yt_dlp/YoutubeDL.py

@@ -1862,11 +1862,10 @@ class YoutubeDL:
             self.to_screen('[download] Downloading item %s of %s' % (
                 self._format_screen(i + 1, self.Styles.ID), self._format_screen(n_entries, self.Styles.EMPHASIS)))
 
-            extra.update({
+            entry_result = self.__process_iterable_entry(entry, download, collections.ChainMap({
                 'playlist_index': playlist_index,
                 'playlist_autonumber': i + 1,
-            })
+            }, extra))
-            entry_result = self.__process_iterable_entry(entry, download, extra)
             if not entry_result:
                 failures += 1
             if failures >= max_failures: