My question involves criminal law for the state of: Georgia

My boyfriend was sentenced at age 17 for criminal damage to property (felony, damage exceeding $500. ). He received 1st offender, and was placed on probation.

He was living with relatives, and a family member called the police saying he was in possession of marijuana, which is a violation of course. Although he never admitted guilt, he was coerced into accepting a 5 do 1 deal. The drug charge was dismissed for lack of evidence, the violation still stood though.

What I am wondering is, if the marijuana charge was dropped, shouldn't that mean he didn't violate? Is it possible for him to get this fixed? If the violation wasn't there, he wouldn't be a "convicted felon" today.
He had a deal that his record would be wiped clean if he didn't violate the probation.