[FFmpegSubtitlesConvertorPP] fix not working when srt is used as the intermediate...

It was trying to use the ttml/dfxp file with ffmpeg, which doesn't have support for them.
I broke it in e04398e397d4a4f7e0d0994355d5a94c22441e7c.

diff --git a/youtube_dl/postprocessor/ffmpeg.py b/youtube_dl/postprocessor/ffmpeg.py
index 22d7ac65ac6fe6e0aedc4c91a101fb8272b9dd97..6daa6a8b46babaade0f3d8e0518aa4ffb1bea727 100644 (file)
--- a/youtube_dl/postprocessor/ffmpeg.py
+++ b/youtube_dl/postprocessor/ffmpeg.py
@@ -508,6 +508,7 @@ class FFmpegSubtitlesConvertorPP(FFmpegPostProcessor):
 
                 with io.open(srt_file, 'wt', encoding='utf-8') as f:
                     f.write(srt_data)
+                old_file = srt_file
 
                 ext = 'srt'
                 subs[lang] = {