Refactor system command.

src/RESTAPI_system_command.cpp

@@ -124,6 +124,7 @@ namespace OpenWifi {
 			    auto Hosts=i->HostSize();
 			    for(uint64_t j=0;j<Hosts;++j) {
 			        auto CertFileName = i->Host(j).CertFile();
+			        if(!CertFileName.empty()) {
 			            auto InsertResult = CertNames.insert(CertFileName);
 			            if(InsertResult.second) {
 			                Poco::JSON::Object  Inner;
@@ -135,6 +136,7 @@ namespace OpenWifi {
 			            }
 			        }
 			    }
+			}
 			Answer.set("certificates", Certificates);
 			ReturnObject(Answer);
 			return;