Order confirmation email not sent during guest checkout about legacydemosite

[mausumi345]

Order confirmation mail is not being send though i am using a registered user.Exception processing template "orderConfirmation-email": Exception evaluating SpringEL expression:
org.springframework.mail.MailPreparationException: Could not prepare mail; nested exception is org.thymeleaf.exceptions.TemplateProcessingException: Exception evaluating SpringEL expression: "customer.username" (orderConfirmation-email:6)
at org.springframework.mail.javamail.JavaMailSenderImpl.send(JavaMailSenderImpl.java:367)
at org.springframework.mail.javamail.JavaMailSenderImpl.send(JavaMailSenderImpl.java:344)
at org.broadleafcommerce.common.email.service.message.MessageCreator.sendMessage(MessageCreator.java:40)
at org.broadleafcommerce.common.email.service.EmailServiceImpl.sendBasicEmail(EmailServiceImpl.java:96)
at org.broadleafcommerce.common.email.service.EmailServiceImpl.sendTemplateEmail(EmailServiceImpl.java:66)
at org.broadleafcommerce.common.email.service.EmailServiceImpl.sendTemplateEmail(EmailServiceImpl.java:73)
at com.evotec.mlsmr.controller.checkout.MyEmailServiceImpl.sendOrderConfirmation(MyEmailServiceImpl.java:31)
at com.evotec.mlsmr.service.checkout.workflow.MyCompleteOrderActivity.execute(MyCompleteOrderActivity.java:22)
at org.broadleafcommerce.core.checkout.service.workflow.CompleteOrderActivity.execute(CompleteOrderActivity.java:26)
at org.broadleafcommerce.core.workflow.SequenceProcessor.doActivities(SequenceProcessor.java:79)
at org.broadleafcommerce.core.checkout.service.CheckoutServiceImpl.performCheckout(CheckoutServiceImpl.java:72)
at org.broadleafcommerce.core.web.controller.checkout.BroadleafCheckoutController.completeSecureCreditCardCheckout(BroadleafCheckoutController.java:416)
at com.evotec.mlsmr.controller.checkout.CheckoutController.completeSecureCreditCardCheckout(CheckoutController.java:140)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)