Fix panic that occurs when using sensitive count (#1456)

Author: wata727

tflint/runner_eval.go

@@ -159,6 +159,7 @@ func (r *Runner) isEvaluableCountArgument(expr hcl.Expression) (bool, error) {
 	if err != nil {
 		return isEvaluableMetaArgumentsOnError(err)
 	}
+	val, _ = val.Unmark()
 
 	count := 1
 	if err := gocty.FromCtyValue(val, &count); err != nil {

tflint/runner_eval_test.go

@@ -897,6 +897,19 @@ resource "null_resource" "test" {
 }`,
 			Expected: 0,
 		},
+		{
+			Name: "count is sensitive",
+			Content: `
+variable "foo" {
+  default = 1
+  sensitive = true
+}
+
+resource "null_resource" "test" {
+  count = var.foo
+}`,
+			Expected: 1,
+		},
 		{
 			Name: "count is unevaluable",
 			Content: `