Handle service worker error in Firefox (#8272)

* Handle service worker error in Firefox

See https://bugzilla.mozilla.org/show_bug.cgi?id=1429714 for more details.

* Update serviceWorker.js

Author: rosinghal

packages/cra-template-typescript/template/src/serviceWorker.ts

@@ -138,8 +138,12 @@ function checkValidServiceWorker(swUrl: string, config?: Config) {
 
 export function unregister() {
   if ('serviceWorker' in navigator) {
-    navigator.serviceWorker.ready.then(registration => {
-      registration.unregister();
-    });
+    navigator.serviceWorker.ready
+      .then(registration => {
+        registration.unregister();
+      })
+      .catch(error => {
+        console.error(error.message);
+      });
   }
 }

packages/cra-template/template/src/serviceWorker.js

@@ -130,8 +130,12 @@ function checkValidServiceWorker(swUrl, config) {
 
 export function unregister() {
   if ('serviceWorker' in navigator) {
-    navigator.serviceWorker.ready.then(registration => {
-      registration.unregister();
-    });
+    navigator.serviceWorker.ready
+      .then(registration => {
+        registration.unregister();
+      })
+      .catch(error => {
+        console.error(error.message);
+      });
   }
 }