various test 🐛 fixes

refs #6550
- cleanup deprecation messages
- fix get `undefined` error in tests

core/client/app/mixins/editor-base-controller.js

@@ -128,6 +128,11 @@ export default Mixin.create({
     hasDirtyAttributes: computed.apply(Ember, watchedProps.concat({
         get() {
             let model = this.get('model');
+
+            if (!model) {
+                return false;
+            }
+
             let markdown = model.get('markdown');
             let title = model.get('title');
             let titleScratch = model.get('titleScratch');

core/client/config/deprecation-workflow.js

@@ -2,6 +2,6 @@ window.deprecationWorkflow = window.deprecationWorkflow || {};
 window.deprecationWorkflow.config = {
     workflow: [
         {handler: 'silence', matchMessage: 'Using the injected `container` is deprecated. Please use the `getOwner` helper instead to access the owner of this object.'},
-        {handler: 'silence', matchMessage: 'You modified (-join-classes \'ember-view\' \'form-group\' (-normalize-class \'errorClass\' errorClass activeClass=undefined inactiveClass=undefined)) twice in a single render. This was unreliable in Ember 1.x and will be removed in Ember 3.0'}
+        {handler: 'silence', matchMessage: 'You modified (-join-classes "ember-view" "form-group" (-normalize-class "errorClass" errorClass activeClass=undefined inactiveClass=undefined)) twice in a single render. This was unreliable in Ember 1.x and will be removed in Ember 3.0'}
     ]
 };