For those who didn't read the article:
Golden's attorney's (Peter Brann's) argument: "Based on my read of the relevant statutes and regulations, if a candidate receives more than 50% of the votes that contain a first choice, RCV is not used to determine the winner. Thus, if the first choice on a ballot is left blank, that would not be considered in determining whether the candidate exceeded the 50% threshold."
Secretary of State's (Shenna Bellows') response: “Under Maine election law, 'blanks' may well include write-ins for someone other than the three official candidates. Given that more than 12,000 voters made a first choice that was not either Congressman Golden or Representative Theriault, it is mathematically possible that the second choices of those voters could change the outcome. For that reason, the law requires that we proceed with the ranked choice voting tabulation."
TL;DR: Should ballots whose first choice is blank be considered when determining whether a candidate exceeded the 50% threshold? Golden says no, Secretary of State says yes.