FIX: exceptions raised when editing replies were not displaying their error messages

app/assets/javascripts/discourse/models/composer.js.es6

@@ -762,14 +762,9 @@ const Composer = RestModel.extend({
       .then(() => {
         // rest model only sets props after it is saved
         post.set("cooked", props.cooked);
-        return post
+        return post.save(props).then(result => {
-          .save(props)
-          .then(result => {
           this.clearState();
           return result;
-          })
-          .catch(error => {
-            throw new Error(error);
         });
       })
       .catch(rollback);