fix: guard resp against nil from http do (#237)

Signed-off-by: Chris Gianelloni <wolf31o2@blinklabs.io>

env.go

@@ -34,7 +34,7 @@ func getNodeMetrics(ctx context.Context) ([]byte, int, error) {
 		cfg.Prometheus.Host,
 		cfg.Prometheus.Port,
 	)
-	var respBodyBytes []byte
+	respBodyBytes := []byte{}
 	// Setup request
 	req, err := http.NewRequest(
 		http.MethodGet,
@@ -56,6 +56,11 @@ func getNodeMetrics(ctx context.Context) ([]byte, int, error) {
 	if err != nil {
 		return respBodyBytes, http.StatusInternalServerError, err
 	}
+	if resp == nil {
+		return respBodyBytes, http.StatusInternalServerError, fmt.Errorf(
+			"empty response",
+		)
+	}
 	// Read the entire response body and close it to prevent a memory leak
 	respBodyBytes, err = io.ReadAll(resp.Body)
 	if err != nil {