Add destroy method to AssetManager

src/asset_manager/index.js

@@ -347,6 +347,15 @@ export default () => {
      */
     onDblClick(func) {
       c.onDblClick = func;
+    },
+
+    destroy() {
+      assets.reset();
+      fu.collection.reset();
+      fu.remove();
+      am.remove();
+      [assets, am, fu].forEach(i => (i = null));
+      c = {};
     }
   };
 };

src/editor/model/Editor.js

@@ -758,7 +758,8 @@ export default Backbone.Model.extend({
       Canvas,
       Keymaps,
       RichTextEditor,
-      LayerManager
+      LayerManager,
+      AssetManager
     } = this.attributes;
     this.stopDefault();
     DomComponents.clear();
@@ -769,6 +770,7 @@ export default Backbone.Model.extend({
     Keymaps.removeAll();
     RichTextEditor.destroy();
     LayerManager.destroy();
+    AssetManager.destroy();
     this.view.remove();
     this.stopListening();
     this.clear({ silent: true });