resource/aws_lb_target_group: Prevent crash from missing matcher during read

[bflad]

Fixes #3949

Interestingly enough, its not reproducible in us-west-2, but does crash in sa-east-1. Maybe they're testing a new service release? Sample config that panics:

provider "aws" {
  region = "sa-east-1"
}

resource "aws_lb_target_group" "example" {
  name     = "example"
  port     = 8082
  protocol = "TCP"
  vpc_id   = "${aws_vpc.example.id}"
}

resource "aws_vpc" "example" {
  cidr_block = "10.0.0.0/16"
}

[tombuildsstuff]

LGTM 👍

[ctso]

We're also seeing this in us-east-1.

[bflad]

This has been released in version 1.13.0 of the AWS provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!