Fix trait update with defined classes in attributes.

src/dom_components/model/Component.js

@@ -481,7 +481,7 @@ export default class Component extends StyleableModel {
   addAttributes(attrs, opts = {}) {
     return this.setAttributes(
       {
-        ...this.getAttributes({ noClass: 1 }),
+        ...this.getAttributes({ noClass: true }),
         ...attrs,
       },
       opts
@@ -568,7 +568,9 @@ export default class Component extends StyleableModel {
     const id = this.getId();
 
     // Add classes
-    if (!opts.noClass) {
+    if (opts.noClass) {
+      delete attributes.class;
+    } else {
       this.get('classes').forEach(cls => classes.push(isString(cls) ? cls : cls.get('name')));
       classes.length && (attributes.class = classes.join(' '));
     }

src/trait_manager/model/Trait.js

@@ -133,9 +133,7 @@ export default class Trait extends Model {
     if (this.get('changeProp')) {
       target.set(name, valueToSet, opts);
     } else {
-      const attrs = { ...target.get('attributes') };
-      attrs[name] = valueToSet;
-      target.set('attributes', attrs, opts);
+      target.addAttributes({ [name]: valueToSet }, opts);
     }
   }