fix index error for workers who have not been rated by this requester
fix index error for workers who have not been rated by this requester

crowdresearch/daemo,crowdresearch/daemo,crowdresearch/daemo,crowdresearch/crowdsource-platform,crowdresearch/crowdsource-platform,crowdresearch/daemo,crowdresearch/crowdsource-platform,crowdresearch/crowdsource-platform