Make open assets command trackable

src/commands/view/OpenAssets.js

@@ -31,8 +31,18 @@ module.exports = {
       uploadEl && uploadEl.setAttribute('accept', accept);
     }
 
-    modal.setTitle(title);
-    modal.setContent(amContainer);
-    modal.open();
+    modal
+      .open({
+        title,
+        content: amContainer
+      })
+      .getModel()
+      .once('change:open', () => editor.stopCommand(this.id));
+    return this;
+  },
+
+  stop(editor) {
+    editor.Modal.close();
+    return this;
   }
 };