stats: do not compute the stats if nothing happened in the last log, as goaccess 1.2 fails on that

Signed-off-by: Mattia Rizzolo <mapreri@ubuntu.com>

scripts/stats.ubuntu-it.org

@@ -30,6 +30,11 @@ for dir in "${logdirs[@]}"; do
     sitename=$(basename "$dir")
     if [[ -d "${dir}" ]]; then
         echo "Generating stats for ${sitename}..."
+            if [[ ! -s "$dir/access.log" ]]; then
+                echo "+ access.log for $sitename is empty, reusing the last analysis."
+                cp "/srv/stats.ubuntu-it.org/current/${sitename}.html" "${deploy}/${sitename}.html"
+                continue
+            fi
         # blackhole stderr because that's where the progress counter goes,
         # filling up the log/screen/terminal
         zgrep -h "" "${dir}"/access* | goaccess - \