$goto variable is not define in uc_affiliate2_click_callback()

Hello,

I just found a issue with $goto variable in uc_affiliate2_click_callback function. $goto defining after uc_affiliate2_click_callback been called - so we cant track destination.

So what I did - just move $goto definition above _uc_affiliate2_register_click

  $num_args = func_num_args();
  $goto = '<front>';

  if ($num_args > 1) {
    $args = func_get_args();
    unset($args[0]);

    $goto = join('/', $args);
  }  

  if ($account && _uc_affiliate2_register_click($account, $goto)) {

Please put it into next release.

Thanks,
Vadim