Merge pull request #1874 from matrix-org/luke/fix-analytics-crash

Fix crash when browser doesn't report page change measurement

src/Analytics.js

@@ -164,18 +164,22 @@ class Analytics {
     }
 
     trackPageChange(generationTimeMs) {
-        if (typeof generationTimeMs !== 'number') {
-            throw new Error('Analytics.trackPageChange: expected generationTimeMs to be a number');
-        }
         if (this.disabled) return;
         if (this.firstPage) {
             // De-duplicate first page
             // router seems to hit the fn twice
             this.firstPage = false;
             return;
         }
+
+        if (typeof generationTimeMs === 'number') {
+            this._paq.push(['setGenerationTimeMs', generationTimeMs]);
+        } else {
+            console.warn('Analytics.trackPageChange: expected generationTimeMs to be a number');
+            // But continue anyway because we still want to track the change
+        }
+
         this._paq.push(['setCustomUrl', getRedactedUrl()]);
-        this._paq.push(['setGenerationTimeMs', generationTimeMs]);
         this._paq.push(['trackPageView']);
     }
 

src/components/structures/MatrixChat.js

@@ -413,6 +413,10 @@ export default React.createClass({
         performance.clearMarks('riot_MatrixChat_page_change_start');
         performance.clearMarks('riot_MatrixChat_page_change_stop');
         const measurement = performance.getEntriesByName('riot_MatrixChat_page_change_delta').pop();
+
+        // In practice, sometimes the entries list is empty, so we get no measurement
+        if (!measurement) return null;
+
         return measurement.duration;
     },