Fix schema key is not in entities (paularmstrong#380)

src/__tests__/__snapshots__/index.test.js.snap

@@ -52,6 +52,18 @@ Array [
 ]
 `;
 
+exports[`denormalize set to undefined if schema key is not in entities 1`] = `
+Object {
+  "author": undefined,
+  "comments": Array [
+    Object {
+      "user": undefined,
+    },
+  ],
+  "id": "123",
+}
+`;
+
 exports[`normalize can use fully custom entity classes 1`] = `
 Object {
   "entities": Object {

src/__tests__/index.test.js

@@ -220,6 +220,33 @@ describe('denormalize', () => {
     expect(denormalize('123', article, entities)).toMatchSnapshot();
   });
 
+  test('set to undefined if schema key is not in entities', () => {
+    const user = new schema.Entity('users');
+    const comment = new schema.Entity('comments', {
+      user: user
+    });
+    const article = new schema.Entity('articles', {
+      author: user,
+      comments: [comment]
+    });
+
+    const entities = {
+      articles: {
+        '123': {
+          id: '123',
+          author: '8472',
+          comments: ['1']
+        }
+      },
+      comments: {
+        '1': {
+          user: '123'
+        }
+      }
+    };
+    expect(denormalize('123', article, entities)).toMatchSnapshot();
+  });
+
   test('does not modify the original entities', () => {
     const user = new schema.Entity('users');
     const article = new schema.Entity('articles', { author: user });

src/index.js

@@ -109,7 +109,11 @@ const getEntities = (entities) => {
       return entityOrId;
     }
 
-    return isImmutable ? entities.getIn([schemaKey, entityOrId.toString()]) : entities[schemaKey][entityOrId];
+    if (isImmutable) {
+      return entities.getIn([schemaKey, entityOrId.toString()]);
+    }
+
+    return entities[schemaKey] && entities[schemaKey][entityOrId];
   };
 };