Revision 5415

backport (glarose): bug fix.  when updating to hide set header display I
assumed that the $db->getMergedSet($userToShow, $setID) would succeed,
which isn't the case for a set that isn't assigned to any users (in
particular, which isn't assigned to the instructor who is editing the
set).  this bug fix resolves that by instead using the global set to
determine if headers should be displayed when the call to get the merged
set fails.