fix: fix domain identity not found in output issue (#36)

Co-authored-by: Anmol Nagpal <anmol@clouddrove.com>

outputs.tf

@@ -1,7 +1,7 @@
 ##Module      : DOMAIN IDENTITY
 ## Description : Terraform module to create domain identity using domain
 output "domain_identity_arn" {
-  value       = aws_ses_domain_identity.default[0].arn
+  value       = try(aws_ses_domain_identity.default[0].arn, "")
   description = "ARN of the SES domain identity."
 }