Use computed for atlas detection

src/scenes/DocumentScene/DocumentScene.js

@@ -77,6 +77,11 @@ class DocumentScene extends React.Component {
     if (doc) {
       actions = (
         <div className={ styles.actions }>
+          { store.isAtlas ? (
+            <HeaderAction>
+              <Link to={ `/documents/${doc.id}/new` }>New document</Link>
+            </HeaderAction>
+          ) : null }
           <HeaderAction>
             <Link to={ `/documents/${doc.id}/edit` }>Edit</Link>
           </HeaderAction>
@@ -106,7 +111,7 @@ class DocumentScene extends React.Component {
           </CenteredContent>
         ) : (
           <Flex flex={ true }>
-            { doc.atlas.type === 'atlas' ? (
+            { store.isAtlas ? (
               <div className={ styles.sidebar }>
                 <Tree
                   paddingLeft={20}

src/scenes/DocumentScene/DocumentSceneStore.js

@@ -1,4 +1,4 @@
-import { observable, action } from 'mobx';
+import { observable, action, computed } from 'mobx';
 import { client } from 'utils/ApiClient';
 import { browserHistory } from 'react-router';
 
@@ -8,6 +8,13 @@ const store = new class DocumentSceneStore {
   @observable isFetching = true;
   @observable isDeleting;
 
+  /* Computed */
+
+  @computed get isAtlas() {
+    console.log(this.document.atlas.type)
+    return this.document.atlas.type === 'atlas';
+  }
+
   /* Actions */
 
   @action fetchDocument = async (id) => {