when done exporting with audio, there was an error and it won't work

[MapidsFanAnimator]

Version information

• fluent-ffmpeg version: 2.1.2
• ffmpeg version: 6.0
• OS: Windows 11

Code to reproduce

here is the code that I entered v

const audios = await Movie.getAudio(req.body.id);
    let complexFilterString = "";
    for (const i in audios) {
    const audio = audios[i];
    const baseDuration = audio.stop - audio.start;
    const duration = Math.max(baseDuration, audio.trimEnd) - audio.trimStart;
    console.log(duration, baseDuration)
    ok.input(audio.filepath);
    ok.addInputOptions("-t", frameToSec(duration));
    complexFilterString += `[${i}:a]adelay=` + frameToSec(audio.start - 0) * 1e3 + `[audio${i}];`
     }
    ok
        .complexFilter(complexFilterString + `${audios.map((_, i) => `[audio${i}]`).join("")}amerge[a]`)
        .videoCodec("libx264")
        .audioCodec("aac")
        .outputOptions("-map", "[0:v]")
        .outputOptions("-map", "[a]")
        .outputOptions("-framerate", "23.97")
        .outputOptions("-r", "23.97")
        .output(path.join(base, "output.mp4"))
        .run();
});

and here's the error Error: ffmpeg exited with code 1: Stream specifier ':a' in filtergraph description [0:a]adelay=41.71881518564873[audio0];[audio0]amerge[a] matches no streams.

even when I tried fixing it like added 1:a or something, it still show up an error, how do you fix it?