Add destroy method to Commands module

src/commands/index.js

@@ -424,6 +424,10 @@ export default () => {
       if (!command.stop) command.noStop = 1;
       const cmd = CommandAbstract.extend(command);
       return new cmd(c);
+    },
+
+    destroy() {
+      [em, c, commands, defaultCommands, active].forEach(i => (i = {}));
     }
   };
 };

src/editor/model/Editor.js

@@ -761,7 +761,8 @@ export default Backbone.Model.extend({
       LayerManager,
       AssetManager,
       BlockManager,
-      CodeManager
+      CodeManager,
+      Commands
     } = this.attributes;
     this.stopDefault();
     DomComponents.clear();
@@ -775,6 +776,7 @@ export default Backbone.Model.extend({
     AssetManager.destroy();
     BlockManager.destroy();
     CodeManager.destroy();
+    Commands.destroy();
     this.view.remove();
     this.stopListening();
     this.clear({ silent: true });