fftools/ffmpeg: Fix leak of AVFilterInOut in case of error

The AVFilterInOuts normally get freed in init_output_filter() when
the corresponding streams get created; yet if an error happens before
one reaches said point, they leak. Therefore this commit makes
ffmpeg_cleanup free them, too.

Fixes ticket #8267.
Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

fftools/ffmpeg.c

@@ -528,6 +528,7 @@ static void ffmpeg_cleanup(int ret)
         for (j = 0; j < fg->nb_outputs; j++) {
             OutputFilter *ofilter = fg->outputs[j];
 
+            avfilter_inout_free(&ofilter->out_tmp);
             av_freep(&ofilter->name);
             av_freep(&ofilter->formats);
             av_freep(&ofilter->channel_layouts);