Fix loaf monitoring bug (#3675)

* Fix LoAF monitoring bug

* Add semi colon

Author: tunetheweb

src/static/js/send-web-vitals.js

@@ -1,7 +1,8 @@
 function sendWebVitals() {
 
   function getLoafAttribution(attribution) {
-    if (!attribution?.longAnimationFrameEntries) {
+    const loafEntriesLength = attribution?.longAnimationFrameEntries?.length || 0;
+    if (loafEntriesLength === 0) {
       return {};
     }
 
@@ -10,7 +11,7 @@ function sendWebVitals() {
     };
 
     // The last LoAF entry is usually the most relevant.
-    const loaf = attribution.longAnimationFrameEntries.at(-1)
+    const loaf = attribution.longAnimationFrameEntries.at(-1);
     const loafEndTime = loaf.startTime + loaf.duration;
     loaf.scripts.forEach(script => {
       if (script.duration <= loafAttribution.debug_loaf_script_total_duration) {
@@ -38,7 +39,7 @@ function sendWebVitals() {
         debug_loaf_script_source_char_position: script.sourceCharPosition,
 
         // LoAF metadata.
-        debug_loaf_meta_length: attribution.longAnimationFrameEntries.length,
+        debug_loaf_meta_length: loafEntriesLength,
       }
     });