Check-in button on reservation page only shows for admins

[njm506]

Affects 2.8.6.2

Regular users are unable to check-in on the Edit Reservation page (where the email links to), but they can check in from the dashboard. This is due to an error in the logic (PR to follow):

{if $CheckInRequired && (!checkinAdminOnly || $CanViewAdmin)}

Compiles down to:

<?php
  if (
    $_smarty_tpl->tpl_vars['CheckInRequired']->value &&
    (!'checkinAdminOnly' || $_smarty_tpl->tpl_vars['CanViewAdmin']->value)
  ) {?>

There is a missing $, so a string is used, which always evaluates to true (so the ! always evaluates to false).