AVAssetWriterInput-引起的-crash

如果 asset 中没有音频轨道
却调用了如下方法给 writer 添加了一个 input 就会导致报错:

-[AVAssetWriterInput appendSampleBuffer:] Must start a session (using -[AVAssetWriter startSessionAtSourceTime:) before appending sample buffers'

AVAssetWriterInput *assetWriterAudioInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio outputSettings:[self writerOutputAudioSettings]];
    // Add the input to the writer if possible.
    
    if ([assetWriter canAddInput:assetWriterAudioInput]) {
        [assetWriter addInput:assetWriterAudioInput];
    }