the name of the recordset on the user update p[age is:
SecurityAssisttblusers
the global variable reference on the email template name needs to reference the recordset name that is created.
change:
global $row_SecurityAssistusers;
to use the correct recordset name. there should also be a global for the recordset object as well as one for the row:
global $SecurityAssisttblusers;
global $row_SecurityAssisttblusers;