Fix(cli): guard vela top against nil rest.Config panic (#7279)

K8SVersion, velaCorePodUsage, and velaCLusterGatewayPodUsage in
references/cli/top/model/info.go called kubernetes.NewForConfig /
metrics.NewForConfig without checking for a nil *rest.Config first.
client-go panics with a nil-pointer dereference in that case instead
of returning an error, so vela top crashes instead of showing
Unknown/N/A for those fields.

Confirmed via two independent call paths that both panicked before
this fix: InfoBoard.Init (references/cli/top/component) and
App.Init (references/cli/top/view).

Added regression tests for all three functions with a nil config.

Signed-off-by: sakirr05 <sakirahmed75531@gmail.com>
Co-authored-by: sakirr05 <sakirahmed75531@gmail.com>
(cherry picked from commit 66e9107688)

references/cli/top/model/info.go

@@ -86,6 +86,9 @@ func (i *Info) ClusterNum() string {
 
 // K8SVersion return k8s version info
 func K8SVersion(cfg *rest.Config) string {
+	if cfg == nil {
+		return Unknown
+	}
 	c, err := kubernetes.NewForConfig(cfg)
 	if err != nil {
 		return Unknown
@@ -141,6 +144,9 @@ func ApplicationRunningNum(cfg *rest.Config) string {
 }
 
 func velaCorePodUsage(cfg *rest.Config) (*v1beta1.PodMetrics, error) {
+	if cfg == nil {
+		return nil, errors.New("no rest.Config available")
+	}
 	ctx := context.Background()
 	c, err := metrics.NewForConfig(cfg)
 	if err != nil {
@@ -194,6 +200,9 @@ func VelaCoreRatio(c client.Client, cfg *rest.Config) (string, string, string, s
 }
 
 func velaCLusterGatewayPodUsage(cfg *rest.Config) (*v1beta1.PodMetrics, error) {
+	if cfg == nil {
+		return nil, errors.New("no rest.Config available")
+	}
 	ctx := context.Background()
 	c, err := metrics.NewForConfig(cfg)
 	if err != nil {

references/cli/top/model/info_test.go

@@ -22,6 +22,8 @@ import (
 	. "github.com/onsi/ginkgo/v2"
 	. "github.com/onsi/gomega"
 	"github.com/stretchr/testify/assert"
+
+	clicommon "github.com/oam-dev/kubevela/references/common"
 )
 
 func TestInfo_CurrentContext(t *testing.T) {
@@ -46,6 +48,26 @@ func TestInfo_GOLangVersion(t *testing.T) {
 	assert.Contains(t, GOLangVersion(), "go")
 }
 
+func TestInfo_K8SVersion_NilConfig(t *testing.T) {
+	assert.Equal(t, Unknown, K8SVersion(nil))
+}
+
+func TestInfo_VelaCoreRatio_NilConfig(t *testing.T) {
+	cpuL, memL, cpuR, memR := VelaCoreRatio(nil, nil)
+	assert.Equal(t, clicommon.MetricsNA, cpuL)
+	assert.Equal(t, clicommon.MetricsNA, memL)
+	assert.Equal(t, clicommon.MetricsNA, cpuR)
+	assert.Equal(t, clicommon.MetricsNA, memR)
+}
+
+func TestInfo_CLusterGatewayRatio_NilConfig(t *testing.T) {
+	cpuL, memL, cpuR, memR := CLusterGatewayRatio(nil, nil)
+	assert.Equal(t, clicommon.MetricsNA, cpuL)
+	assert.Equal(t, clicommon.MetricsNA, memL)
+	assert.Equal(t, clicommon.MetricsNA, cpuR)
+	assert.Equal(t, clicommon.MetricsNA, memR)
+}
+
 var _ = Describe("test info", func() {
 	It("running app num", func() {
 		Expect(ApplicationRunningNum(cfg)).To(Equal("1/1"))