Mail displays code call if there is no matching field in the content

Created a template that will mail a digest newsletter of recent content to subscribers (using the subscription module).

Not all of my content types have all the same custom fields. Notably, most content has a subhead (called by the template with !cckvalue1_field_sub_headline) but events do not.

When an event posts to the newsletter, instead of skipping the call for the non-existent field or producing a blank line, the template simply echoes back the call for the content (!cckvalue1_field_sub_headline).

Needless to say, this is not what I want to be sending out to people.