Когда std :: vector :: pop_back может генерировать исключение [duplicate]

import javax.mail.internet.MimeMessage;
import org.springframework.mail.javamail.MimeMessageHelper;

MimeMessage mimeMessage = mailSender.createMimeMessage();
MimeMessageHelper helper = new MimeMessageHelper(mimeMessage, false, "utf-8");
String htmlMsg = "<h3>Hello World!</h3>";
mimeMessage.setContent(htmlMsg, "text/html");
helper.setTo("someone@abc.com");
helper.setSubject("This is the test message for testing gmail smtp server using spring mail");
helper.setFrom("abc@gmail.com");
mailSender.send(mimeMessage);