fix import dpd_timeout error (#1597)

* fix import dpd_timeout error

* add changelog

---------

Co-authored-by: mikatong <mikatong@tencent.com>

Author: tongyiming

.changelog/1597.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+resource/tencentcloud_vpn_connection: fix dpd_timeout read error
+```

tencentcloud/resource_tc_vpn_connection.go

@@ -671,11 +671,14 @@ func resourceTencentCloudVpnConnectionRead(d *schema.ResourceData, meta interfac
 	_ = d.Set("health_check_remote_ip", *connection.HealthCheckRemoteIp)
 	// dpd
 	_ = d.Set("dpd_enable", *connection.DpdEnable)
-	dpdTimeoutInt, err := strconv.Atoi(*connection.DpdTimeout)
-	if err != nil {
-		return err
+	if *connection.DpdTimeout != "" {
+		dpdTimeoutInt, err := strconv.Atoi(*connection.DpdTimeout)
+		if err != nil {
+			return err
+		}
+		_ = d.Set("dpd_timeout", dpdTimeoutInt)
 	}
-	_ = d.Set("dpd_timeout", dpdTimeoutInt)
+
 	_ = d.Set("dpd_action", *connection.DpdAction)
 
 	//tags

tencentcloud/resource_tc_vpn_connection_test.go

@@ -11,7 +11,7 @@ import (
 	vpc "github.com/tencentcloud/tencentcloud-sdk-go/tencentcloud/vpc/v20170312"
 )
 
-func TestAccTencentCloudVpnConnection_basic(t *testing.T) {
+func TestAccTencentCloudVpnConnectionResource_basic(t *testing.T) {
 	t.Parallel()
 	resource.Test(t, resource.TestCase{
 		PreCheck:     func() { testAccPreCheck(t) },