message error tweaks

ui/lib/core/addon/components/message-error.js

@@ -34,15 +34,15 @@ class MessageError extends Component {
           return e;
         });
       }
-      return [adapterError.message];
+      return adapterError.message;
     }
     if (errorMessage) {
-      return [errorMessage];
+      return errorMessage;
     }
     if (errors && errors.length > 0) {
       return errors;
     }
-    return 'no error';
+    return null;
   }
 }
 

ui/lib/core/addon/templates/components/message-error.hbs

-{{#if this.displayErrors.length}}
+{{#if this.displayErrors}}
   {{#each this.displayErrors as |error|}}
     <AlertBanner @type="danger" @message={{error}} data-test-error />
   {{/each}}