Add a default state for metadata

packages/fastboot/src/ember-app.js

@@ -301,7 +301,7 @@ class EmberApp {
     let bootOptions = buildBootOptions(shouldRender);
     let fastbootInfo = new FastBootInfo(req, res, {
       hostWhitelist: this.hostWhitelist,
-      metadata: options.metadata,
+      metadata: options.metadata || {},
     });
 
     let doc = bootOptions.document;

test-packages/basic-app/app/router.js

@@ -15,4 +15,5 @@ Router.map(function() {
   this.route('async-content');
   this.route('echo-request-headers');
   this.route('return-status-code-418');
+  this.route('metadata');
 });

test-packages/basic-app/app/routes/metadata.js

@@ -0,0 +1,12 @@
+import Route from '@ember/routing/route';
+import { inject as service } from '@ember/service';
+
+export default Route.extend({
+  fastboot: service(),
+
+  model() {
+    if (this.get('fastboot.isFastBoot') && this.fastboot.metadata) {
+      return 'test fastboot metadata';
+    }
+  },
+});

test-packages/basic-app/app/templates/metadata.hbs

@@ -0,0 +1 @@
+{{this.model}}

test-packages/integration-tests/test/basic-test.js

@@ -186,4 +186,20 @@ describe("FastBoot", function() {
       .then((r) => r.html());
     expect(html).to.match(/foo from sandbox: 5/);
   });
+
+  it("does not break the render with empty metadata", async function() {
+    const fastboot = new FastBoot({
+      distPath: await buildDist("basic-app"),
+    });
+
+    return fastboot
+      .visit("/metadata", {
+        request: dummyRequest(),
+        response: dummyResponse(),
+      })
+      .then((r) => r.html())
+      .then((html) => {
+        expect(html).to.match(/test fastboot metadata/);
+      });
+  });
 });