Avoid crashing when AudioContext is not available. (#5641)

#4942. We've also had a number of crash reports show up in our logs related to this. Typically we see "undefined is not a constructor" because of the `window.AudioContext || window.webkitAudioContext` returns `undefined`.

app/javascript/shared/helpers/AudioNotificationHelper.js

@@ -5,17 +5,21 @@ import { showBadgeOnFavicon } from './faviconHelper';
 
 export const initOnEvents = ['click', 'touchstart', 'keypress', 'keydown'];
 export const getAlertAudio = async (baseUrl = '', type = 'dashboard') => {
-  const audioCtx = new (window.AudioContext || window.webkitAudioContext)();
+  const audioCtx = getAudioContext();
+
   const playsound = audioBuffer => {
     window.playAudioAlert = () => {
+      if (audioCtx) {
         const source = audioCtx.createBufferSource();
         source.buffer = audioBuffer;
         source.connect(audioCtx.destination);
         source.loop = false;
         source.start();
+      }
     };
   };
 
+  if (audioCtx) {
     const resourceUrl = `${baseUrl}/audio/${type}/ding.mp3`;
     const audioRequest = new Request(resourceUrl);
 
@@ -28,6 +32,19 @@ export const getAlertAudio = async (baseUrl = '', type = 'dashboard') => {
       .catch(() => {
         // error
       });
+  }
+};
+
+export const getAudioContext = () => {
+  let audioCtx;
+
+  try {
+    audioCtx = new (window.AudioContext || window.webkitAudioContext)();
+  } catch {
+    // AudioContext is not available.
+  }
+
+  return audioCtx;
 };
 
 export const notificationEnabled = (enableAudioAlerts, id, userId) => {