I finally read New Titans #100. Raven kills the pastor after the vows.
It’s a common misconception that the officiant “marries” the couple—but it actually the couple that confers the marriage on each other with legally operative words, i.e., the vows.
Those words happened with the exchange of vows and rings—all the officiant was doing was confirming that it happened when interrupted. So it doesn’t affect the validity of the marriage.
So Nightwing and Starfire are married in pre-New 52 continuity, even if they don’t realize it!