Avoid possible error when reading groups in debug mode

Author: westonruter

plugins/optimization-detective/detect.js

@@ -555,7 +555,7 @@ export default async function detect( {
 	const { log, warn, error } = logger;
 	compressionEnabled = gzdecodeAvailable;
 
-	if ( isDebug ) {
+	if ( isDebug && Array.isArray( urlMetricGroupCollection?.groups ) ) {
 		const allUrlMetrics = /** @type Array<UrlMetricDebugData> */ [];
 		for ( const group of urlMetricGroupCollection.groups ) {
 			for ( const otherUrlMetric of group.url_metrics ) {