Hello,
To clairfy, the NULL requests on the "localhost" VirtualHost are requests from browsers like Chrome.
They're pre-connections made by the browser for clients who have already downloaded a webpage from your server.
Basically, the browsers will know that there are links in the webpage that the client may click, so to save time, the browser connects to apache in anticipation of a link being clicked.
However, a request is not yet made, so the browser will simply idle on that connection until the request is made (link is clicked).
During that idle time, apache doesn't know which VirtualHost the connection is for (since the browser has not yet said anything), thus it defaults to the first VH in the list.. which has a ServerName of "localhost".. .. and since no request has been made, the request is NULL.
So you can ignore these entries. They're normal.
No need to change your Apache version.
John