Hi, good morning, I get the following error in the logs "Error message: List index out of bounds: 0" on line 52 of the code. 
This is the code of line 52, how can I validate or how can I fix the error?
 

new CampaignMembersService_SV().constructRegistrantCampaignMember(regData.optIn, newCon,ProfHubEmailSendSelector_SV.newInstance().selectByMasterLabel(new Set<String> {countryMap.get(regData.country)})[0].Communication_Optin__c, uow);

Thanks!