Fix undefined

Author: timfish

packages/browser/src/tracing/browserTracingIntegration.ts

@@ -782,7 +782,7 @@ export function getMetaContent(metaName: string): string | undefined {
 /** Returns the description of a server timing entry */
 export function getServerTiming(name: string): string | undefined {
   const navigation = WINDOW.performance?.getEntriesByType?.('navigation')[0] as PerformanceNavigationTiming | undefined;
-  const entry = navigation?.serverTiming.find(entry => entry.name === name);
+  const entry = navigation?.serverTiming?.find(entry => entry.name === name);
   return entry?.description;
 }