Error about finding no audio stream for video-only files

[0n-s]

[✔] Scanning 'test.mp4'
[✔] Container: QuickTime / MOV [mov,mp4,m4a,3gp,3g2,mj2]
[✘] Could not find audio stream

This is generally fine. Sometimes there are videos included with album downloads, & those videos may not have sound. It's not correct to give an error about not finding an audio track for a file that's not supposed to have one & that's almost always the case (FFmpeg decodes seemingly anything & everything, so if there was supposed to be an audio track, it'd find it). Please demote this to a warning.

[complexlogic]

I agree and am going to push a commit changing the behavior.