fix(vpn): [119233734] modify vpn-gw change (#2778)

* fix: modify vpn gw change

* feat: add changelog

* fix: fmt

Author: gitmkn

.changelog/2778.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+resource/tencentcloud_vpn_gateway: Optimize VPN gateway change issue.
+```

tencentcloud/services/vpn/resource_tc_vpn_gateway.go

@@ -287,7 +287,11 @@ func resourceTencentCloudVpnGatewayRead(d *schema.ResourceData, meta interface{}
 	_ = d.Set("type", gateway.Type)
 	_ = d.Set("create_time", gateway.CreatedTime)
 	_ = d.Set("state", gateway.State)
-	_ = d.Set("prepaid_renew_flag", gateway.RenewFlag)
+	if gateway.RenewFlag != nil {
+		_ = d.Set("prepaid_renew_flag", *gateway.RenewFlag)
+	} else {
+		_ = d.Set("prepaid_renew_flag", svcvpc.VPN_PERIOD_PREPAID_RENEW_FLAG_AUTO_NOTIFY)
+	}
 	_ = d.Set("charge_type", gateway.InstanceChargeType)
 	_ = d.Set("expired_time", gateway.ExpiredTime)
 	_ = d.Set("is_address_blocked", gateway.IsAddressBlocked)