wait for load event before registering service worker

src/app/Coriolis.jsx

@@ -324,6 +324,7 @@ export default class Coriolis extends React.Component {
     // Listen for appcache updated event, present refresh to update view
     // Check that service workers are registered
     if ('serviceWorker' in navigator) {
+      window.addEventListener('load', () => {
         // Your service-worker.js *must* be located at the top-level directory relative to your site.
         // It won't be able to control pages unless it's located at the same level or higher than them.
         // *Don't* register service worker file in, e.g., a scripts/ sub-directory!
@@ -363,6 +364,7 @@ export default class Coriolis extends React.Component {
         }).catch(function(e) {
           console.error('Error during service worker registration:', e);
         });
+      });
     }
     window.onerror = this._onError.bind(this);
     window.addEventListener('resize', () => this.emitter.emit('windowResize'));