customizing errors results in two error rows

[tmcgrath]

I'm trying to customize the error results:

   def afterBindRow(obj, row, index, columns, params, importLogId) {

        if (row[POPID]) {
                def clientSplitPopulation = Population.findByName(row[POPID])
                if (clientSplitPopulation) {
                    obj.population = clientSplitPopulation
                }
                else {
                    importsLogger.logErrorRow(importLogId, row, index, 'something bad happened')
                }
        }
    }

But this results in two error rows for the same error.

What am I doing wrong?

Thanks,
Todd