ffmpeg command fails if there is no video stream

[opheliagame]

ffmpeg command: -ss 853.783 -t 9.629000000000019 -i https://media.v2.pad.ma/DWN/240p1.webm -filter_complex [0:v]scale=640:480:force_original_aspect_ratio=decrease,pad=640:480:-1:-1,setsar=1[v0]; [v0][0:a]concat=n=1:v=1:a=1[v][a] -map [v] -map [a] /opt/render/project/src/f2cc5334-5c9c-49e1-a961-4b97196994f7.mp4

stderr: Stream specifier ':v' in filtergraph description [0:v]scale=640:480:force_original_aspect_ratio=decrease,pad=640:480:-1:-1,setsar=1[v0]; [v0][0:a]concat=n=1:v=1:a=1[v][a] matches no streams