I try to validate low latency HLS fragmented MP4 setup with meadistreamvalidator. I get following error: Error: Invalid URL Detail: '(null)' is not a valid URL Source: mediaplaylistURL.m3u8 - segmentURL.mp4 meadistreamvalidator version is 1.23.14 What does that error mean?

I have a low latency hls with fragmented mp4 setup. When I try to validate it with mediavalidatorstream tool, it gives following error: Detail: '(null)' is not a valid URL Source: media playlisturl - segment url in that playlist What does that error mean?