user_save requires account parameter to have status property defined

I am also having this issue.
It seems this would only be a matter of changing line 547 from
if (isset($edit['status']) && $edit['status'] != $account->status) {
to
if (isset($edit['status']) && isset($account->status) && $edit['status'] != $account->status) {

The sample code above doesn't cause this error because you're not attempting to set status (which is where the notice comes from). Here's real sample code

$account = new stdClass;
$account->uid = 3;
$fields['status'] = 0;
$account = user_save($account, $fields);

In this case, I think the correct fix is to check the status being saved (in $edit) against the $user that was just loaded, not the one passed in $account.

      // Refresh user object.   
      $user = user_load($account->uid, TRUE);
      // Make the original, unchanged user account available to update hooks.
      if (isset($account->original)) {
        $user->original = $account->original;
      }

      // Send emails after we have the new user object.
      if (isset($edit['status']) && $edit['status'] != $user->status) { // <============ changed from $account->status
        // The user's status is changing; conditionally send notification email.
        $op = $edit['status'] == 1 ? 'status_activated' : 'status_blocked';
        _user_mail_notify($op, $user);
      }

#2: user-save-status-change-1049090.patch queued for re-testing.

There are other problems in the same area - this is probably covered by #999004: user_save() relies on $edit instead of $account.