"Forward Mailing" feature results in Smarty error
I just noticed on Civi 5.36.1 + WordPress 5.7.1 that the "Forward Mailing" feature does not work correctly: after I click on the 'forward' link in a received mailing, it takes me to the civi page where I can enter in email addresses to forward the mailing to. After entering an email address, I press the "Forward" button, I just get a WP page that says There has been a critical error on this website.
The webserver error logs contain the following (slightly redacted) associated entries:
[Thu May 06 18:31:42.466433 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: PHP Fatal error: Smarty error: [in string:<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466519 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: <html xmlns="http://www.w3.org/1999/xhtml"><head>, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466553 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466576 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: <meta name="viewport" content="initial-scale=1.0">, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466597 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: <meta name="format-detection" content="telephone=no">, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466613 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: <title>[subject]</title>, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466628 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: , referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466643 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: <style type="text/css">, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466657 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: body{ Margin: 0; padding: 0; }, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466672 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: img{ border: 0px; display: block; }, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466687 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: .socialLinks{ font-size: 6px; }, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466709 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: .socialLinks a{, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466723 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: display: inline-block;, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466738 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: }, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466770 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: .socialIcon{, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466785 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: display: inline-block;, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466800 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: vertical-align: top;, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466814 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: padding-bottom: 0px;, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466829 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: border-radius: 100%;, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466843 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: }, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466857 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: .oldwebkit{ max-width: 570px; }, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466908 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: td.vb-outer{ padding-left: 9px; padding-right: 9px; }, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4
[Thu May 06 18:31:42.466923 2021] [fcgid:warn] [pid 19485:tid 4146279196416] [client x.x.x.x:39364] mod_fcgid: stderr: table.vb-container, table.vb-row, table. in /home/data2/mywebsite.com/wp-content/plugins/civicrm/civicrm/packages/Smarty/Smarty.class.php on line 1100, referer: https://mywebsite.com/civicrm/mailing/forward/?reset=1&jid=111&qid=2117&h=a267e50acef0d4e4