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

@@ -5,29 +5,46 @@ 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 = () => {
-      const source = audioCtx.createBufferSource();
-      source.buffer = audioBuffer;
-      source.connect(audioCtx.destination);
-      source.loop = false;
-      source.start();
+      if (audioCtx) {
+        const source = audioCtx.createBufferSource();
+        source.buffer = audioBuffer;
+        source.connect(audioCtx.destination);
+        source.loop = false;
+        source.start();
+      }
     };
   };
 
-  const resourceUrl = `${baseUrl}/audio/${type}/ding.mp3`;
-  const audioRequest = new Request(resourceUrl);
+  if (audioCtx) {
+    const resourceUrl = `${baseUrl}/audio/${type}/ding.mp3`;
+    const audioRequest = new Request(resourceUrl);
 
-  fetch(audioRequest)
-    .then(response => response.arrayBuffer())
-    .then(buffer => {
-      audioCtx.decodeAudioData(buffer).then(playsound);
-      return new Promise(res => res());
-    })
-    .catch(() => {
-      // error
-    });
+    fetch(audioRequest)
+      .then(response => response.arrayBuffer())
+      .then(buffer => {
+        audioCtx.decodeAudioData(buffer).then(playsound);
+        return new Promise(res => res());
+      })
+      .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) => {