FIX: don't set properties on destroyed components

app/assets/javascripts/discourse/components/d-editor.js.es6

@@ -279,6 +279,7 @@ export default Ember.Component.extend({
     const markdownOptions = this.get('markdownOptions') || {};
 
     cookAsync(value, markdownOptions).then(cooked => {
+      if (this.get('isDestroyed')) { return; }
       this.set('preview', cooked);
       Ember.run.scheduleOnce('afterRender', () => {
         if (this._state !== "inDOM") { return; }

plugins/discourse-presence/assets/javascripts/discourse/components/composer-presence-display.js.es6

@@ -73,6 +73,7 @@ export default Ember.Component.extend({
       previous: this.get('previousState'),
       current: this.get('currentState')
     }).then(r => {
+      if (this.get('isDestroyed')) { return; }
       this.set('presenceUsers', r.users);
       this.set('channel', r.messagebus_channel);
       this.messageBus.subscribe(r.messagebus_channel, message => {