In order to avoid the notice:

PHP Notice: Undefined offset: 2 in /htdocs/sites/all/modules/quickstats/quickstats.module on line 35

you could change the line:

if ($arg[0] == 'node' && is_numeric($arg[1]) && !$arg[2]) {

to:

if ($arg[0] == 'node' && is_numeric($arg[1]) && !isset($arg[2])) {

Best,
/Johs.