fix panic in HCL dup warning (#30780)

Author: bosouza

vault/logical_system.go

@@ -3682,6 +3682,9 @@ func (b *SystemBackend) handlePoliciesSet(policyType PolicyType) framework.Opera
 		}
 
 		if duplicate {
+			if resp == nil {
+				resp = &logical.Response{}
+			}
 			// TODO (HCL_DUP_KEYS_DEPRECATION): remove log and API Warning once the deprecation is done
 			b.logger.Warn("newly created HCL policy contains duplicate attributes, which will no longer be supported in a future version", "policy", policy.Name, "namespace", ns.Path)
 			resp.AddWarning("policy contains duplicate attributes, which will no longer be supported in a future version")

vault/logical_system_test.go

@@ -2817,8 +2817,8 @@ func TestSystemBackend_writeHCLDuplicateAttributes(t *testing.T) {
 
 	// policy with duplicate attribute
 	rules := `path "foo/" { policy = "read" policy = "read" }`
-	req := logical.TestRequest(t, logical.UpdateOperation, "policy/Foo")
-	req.Data["rules"] = rules
+	req := logical.TestRequest(t, logical.UpdateOperation, "policy/foo")
+	req.Data["policy"] = rules
 	resp, err := b.HandleRequest(namespace.RootContext(nil), req)
 	// TODO (HCL_DUP_KEYS_DEPRECATION): change this test to expect an error when creating a policy with duplicate attributes
 	if err != nil {