Allow users to escape error pages with the back button

ui/app/routes/application.js

@@ -11,6 +11,7 @@ export default Route.extend({
 
   actions: {
     didTransition() {
+      this.controllerFor('application').set('error', null);
       window.scrollTo(0, 0);
     },
 

ui/tests/acceptance/application-errors-test.js

+import { find, visit } from 'ember-native-dom-helpers';
+import moduleForAcceptance from 'nomad-ui/tests/helpers/module-for-acceptance';
+import { test } from 'qunit';
+
+moduleForAcceptance('Acceptance | application errors ', {
+  beforeEach() {
+    server.create('agent');
+    server.create('node');
+    server.create('job');
+  },
+});
+
+test('transitioning away from an error page resets the global error', function(assert) {
+  server.pretender.get('/v1/nodes', () => [403, {}, null]);
+
+  visit('/nodes');
+
+  andThen(() => {
+    assert.ok(find('.error-message'), 'Application has errored');
+  });
+
+  visit('/jobs');
+
+  andThen(() => {
+    assert.notOk(find('.error-message'), 'Application is no longer in an error state');
+  });
+});