fix: dont prematurely close transaction

internal/service/transaction.go

@@ -56,7 +56,9 @@ func (s TransactionImpl) Add(tx *sqlx.Tx, user *types.User, transactionInput typ
 	}
 
 	var err error
+	ownsTransaction := false
 	if tx == nil {
+		ownsTransaction = true
 		tx, err = s.db.Beginx()
 		err = db.TransformAndLogDbError("transaction Add", nil, err)
 		if err != nil {
@@ -104,11 +106,13 @@ func (s TransactionImpl) Add(tx *sqlx.Tx, user *types.User, transactionInput typ
 		}
 	}
 
+	if ownsTransaction {
 		err = tx.Commit()
 		err = db.TransformAndLogDbError("transaction Add", nil, err)
 		if err != nil {
 			return nil, err
 		}
+	}
 
 	return transaction, nil
 }