followup to previous patch - don't use TMPL_IF EXPR

followup to previous patch - don't use TMPL_IF EXPR

Because of the way that HTML::Template::Pro evaluates
expressions, any variable referred to in a TMPL_IF EXPR
must be be present when the template is parsed, otherwise
you get Apache error log warnings like this:

non-initialized variable new_subfield

For a simple flag check, TMPL_IF NAME="new_subfield" is sufficient.

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>
Signed-off-by: Henri-Damien LAURENT <henridamien.laurent@biblibre.com>