I have seen a few 404 errors when ads.txt is requested on some of the sites that I manage. I Guess the answer may be identical to the question about an empty robots.txt file or no file at all (just prevent some 404 errors). However I'm having dificuilty to understand the underlying concepts behind ads.txt.
The official help page at IAB is confusing, for example
"When a brand advertiser buys media programmatically, they rely on the fact that the URLs they purchase were legitimately sold by those publishers."
"advertisers buy media" sounds like hiring an atrist to make compelling text, graphics and animations, but does not fit with the context (it's unlikely one would hire artists programatically). "URLs sold by publishers" does not look like they are talking about registering an URL at an isp or ICANN. Publishers generally don't sell URLs unless they quit publishing.
Obviously this is a foreign domain specific language. So could anyone explain what impact an empty ads.txt file could have? Some concerns would be: