add list with an empty string, necessary for terraform 0.12 destroy (#52)

Author: schollii

output.tf

@@ -29,7 +29,8 @@ output "dynamodb_table_id" {
   value = element(
     coalescelist(
       aws_dynamodb_table.with_server_side_encryption.*.id,
-      aws_dynamodb_table.without_server_side_encryption.*.id
+      aws_dynamodb_table.without_server_side_encryption.*.id,
+      [""]
     ),
     0
   )
@@ -40,7 +41,8 @@ output "dynamodb_table_arn" {
   value = element(
     coalescelist(
       aws_dynamodb_table.with_server_side_encryption.*.arn,
-      aws_dynamodb_table.without_server_side_encryption.*.arn
+      aws_dynamodb_table.without_server_side_encryption.*.arn,
+      [""]
     ),
     0
   )