Panic when creating StackSet Instances

[asantos-fuze]

I'm getting a panic when deploying CFn StackSet as SERVICE_MANAGED and callas: DELEGATED_ADMIN

DEBUG: Creating stack set
Stack set has been created successfuly with ID: stack-set-name:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
DEBUG: ConfigData is valid

DEBUG: Stack Set Instances Configuration:
{
	"Regions": [
		"us-east-1"
	],
	"Accounts": null,
	"DeploymentTargets": {
		"AccountFilterType": "",
		"Accounts": null,
		"AccountsUrl": null,
		"OrganizationalUnitIds": [
			"r-xxxxxxxx"
		]
	},
	"OperationPreferences": null,
	"StackSetName": "stack-set-name",
	"CallAs": "DELEGATED_ADMIN"
}

DEBUG: Creating stack set instances
DEBUG: Create stack instances API result:
{
	"OperationId": "yyyyyyyy-yyyy-yyyy-yyyy-yyyyyyyyyyyy",
	"ResultMetadata": {}
}
Submitted CREATE instances operation with ID: yyyyyyyy-yyyy-yyyy-yyyy-yyyyyyyyyyyy
panic: error while creating stack set instances: operation error CloudFormation: DescribeStackSetOperation, https response error StatusCode: 404, RequestID: zzzzzzzz-zzzz-zzzz-zzzz-zzzzzzzzzzzz, StackSetNotFoundException: StackSet stack-set-name not found [recovered]
	panic: error while creating stack set instances: operation error CloudFormation: DescribeStackSetOperation, https response error StatusCode: 404, RequestID: zzzzzzzz-zzzz-zzzz-zzzz-zzzzzzzzzzzz, StackSetNotFoundException: StackSet stack-set-name not found

goroutine 1 [running]:
github.com/aws-cloudformation/rain/internal/cmd.execute.func1()
	/__w/rain/rain/internal/cmd/wrap.go:77 +0x164
panic({0x10460e400?, 0x1400029b400?})
	/usr/local/go/src/runtime/panic.go:792 +0x124
github.com/aws-cloudformation/rain/internal/cmd/stackset.createStackSet({0x0, 0x14000443710, {0x0, 0x1400000c420, {0x1400041d750, 0xf}, {0x14000422d80, 0x2, 0x2}, 0x140004075b0, ...}, ...})
	/__w/rain/rain/internal/cmd/stackset/stackset_deploy.go:361 +0x56c
github.com/aws-cloudformation/rain/internal/cmd/stackset.init.func1(0x1400025b800?, {0x14000200210?, 0x2?, 0x103837510?})
	/__w/rain/rain/internal/cmd/stackset/stackset_deploy.go:144 +0x780
github.com/spf13/cobra.(*Command).execute(0x104e43640, {0x14000200160, 0xb, 0xb})
	/go/pkg/mod/github.com/spf13/cobra@v1.9.1/command.go:1019 +0x810
github.com/spf13/cobra.(*Command).ExecuteC(0x104e3eec0)
	/go/pkg/mod/github.com/spf13/cobra@v1.9.1/command.go:1148 +0x350
github.com/spf13/cobra.(*Command).Execute(...)
	/go/pkg/mod/github.com/spf13/cobra@v1.9.1/command.go:1071
github.com/aws-cloudformation/rain/internal/cmd.execute(0x68?)
	/__w/rain/rain/internal/cmd/wrap.go:86 +0x4c
github.com/aws-cloudformation/rain/internal/cmd.Execute(0x104dba3c8?)
	/__w/rain/rain/internal/cmd/wrap.go:95 +0x1c
main.main()
	/__w/rain/rain/cmd/rain/main.go:23 +0x24

I believe the issue happens because the StackSet is DELEGATED_ADMIN and no callas parameter is being passed on the function:

rain/internal/aws/cfn/stacksets.go

Line 404 in 251173d

operation, err = getClient().DescribeStackSetOperation(context.Background(), &cloudformation.DescribeStackSetOperationInput{