[FFmpeg-user] Cannot find a matching stream for unlabeled input pad 7 on filter Parsed_concat_2

[Randy Johnson]

Hello,

This seems similiar to the other issue I posted last night.  I was able
to get that issue resolved but now I am getting this error:

Cannot find a matching stream for unlabeled input pad 7 on filter
Parsed_concat_2

when running this command:

ffmpeg \
-loop 1 -framerate 30 -t 1.32 \
-i filler640480.jpg \
-i f.mp4 -y \
-loop 1 -framerate 30 -t -451.356 \
-i filler640480.jpg \
-i 9.mp4 -y \
-f lavfi -t 0.1 -i anullsrc=channel_layout=mono:sample_rate=48000 \
-filter_complex
"[0:v]setsar=1[v0];[2:v]setsar=1[v1];[v0][4:a][v1][4:a]concat=n=4:v=1:a=1"
-vsync 2 0225-grid.mp4

Any idea what is going on with this error?

Thank You,

Randy