handle nil private key in http client init

pkg/enterpriseclient/client.go

@@ -25,13 +25,15 @@ func New(privateKeyContents []byte) *HTTPClient {
 }
 
 func NewHTTPClient(origin string, privateKeyContents []byte) *HTTPClient {
-	privateKey, err := decodePrivateKeyPEM(privateKeyContents)
-	if err != nil {
-		privateKey = nil
-	}
 	c := &HTTPClient{
-		privateKey: privateKey,
-		apiOrigin:  origin,
+		apiOrigin: origin,
+	}
+	if privateKeyContents != nil {
+		privateKey, err := decodePrivateKeyPEM(privateKeyContents)
+		if err != nil {
+			privateKey = nil
+		}
+		c.privateKey = privateKey
 	}
 
 	return c

pkg/enterpriseclient/client_test.go

@@ -0,0 +1,16 @@
+package enterpriseclient
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewNilHTTPClient(t *testing.T) {
+	req := require.New(t)
+	client := NewHTTPClient("origin", nil)
+	req.Equal(&HTTPClient{
+		privateKey: nil,
+		apiOrigin:  "origin",
+	}, client)
+}