Nil out a closed logfile.

apt-panopticommon.lua

@@ -424,6 +424,7 @@ APT.logPost = function()
     if nil ~= APT.logFile then
 	APT.logFile:write("</body></html> \n")
 	APT.logFile:close()
+	APT.logFile = nil
     end
 end