ffmpeg: check for unconnected outputs

Fixes e.g.:

ffmpeg -f lavfi -i testsrc -f lavfi -i testsrc -filter_complex "[0:v][1:v]psnr[out]" -f null none

1 files changed, 2 insertions, 0 deletions

diff --git a/ffmpeg_opt.c b/ffmpeg_opt.c
index d1fe8742ff..e73a61059f 100644
--- a/ffmpeg_opt.c
+++ b/ffmpeg_opt.c
@@ -3260,6 +3260,8 @@ int ffmpeg_parse_options(int argc, char **argv)
         goto fail;
     }
 
+    check_filter_outputs();
+
 fail:
     uninit_parse_context(&octx);
     if (ret < 0) {