Pass ModalManagerState into Modal instances instead of calling the global.

js/src/common/components/Modal.js

@@ -31,7 +31,7 @@ export default class Modal extends Component {
     // If the global modal state currently contains a modal,
     // we've just opened up a new one, and accordingly,
     // we don't need to show a hide animation.
-    if (!app.modal.modal) {
+    if (!this.attrs.state.modal) {
       this.attrs.onhide();
     }
   }
@@ -112,7 +112,7 @@ export default class Modal extends Component {
    * Hide the modal.
    */
   hide() {
-    app.modal.close();
+    this.attrs.state.close();
   }
 
   /**