Email subject w/ tag gets blanked if tag is blank

I have a contact form configured to omit lines in which a tag is blank.

This setting seems to apply to the subject line as well. I am using Contact Forms for a feedback form in which a person’s name is optional. The subject line of the email is configured as:

2017 Advice [your-name]

When the person declines to include their name, the subject line is blanked entirely.

Expected behavior: the “omit lines with blank tags” setting should apply only to body text, and not to the subject line