fix string comparison when empty
fix string comparison when empty

alexfrolov/grappa,uwsampa/grappa,uwsampa/grappa,alexfrolov/grappa,buaasun/grappa,uwsampa/grappa,uwsampa/grappa,buaasun/grappa,alexfrolov/grappa,buaasun/grappa,buaasun/grappa,alexfrolov/grappa,alexfrolov/grappa,buaasun/grappa,alexfrolov/grappa,uwsampa/grappa,uwsampa/grappa,uwsampa/grappa,buaasun/grappa,alexfrolov/grappa,buaasun/grappa