I had ignored the same error for the 2 months I have had an Ubuntu server. I found this post nicely solved the error. Thank you Michael!.
As did you Jay, I found the culprit at /etc/apache2/ports.conf . I tried simply this:
# NameVirtualHost *:80
I only commented out that line and no other changes and no more
“NameVirtualHost *:80 has no VirtualHosts”