FIX: ensures category url of category drop is built using slug and id (#9069)

app/assets/javascripts/select-kit/components/category-drop.js.es6

@@ -155,18 +155,16 @@ export default ComboBoxComponent.extend({
   },
 
   actions: {
-    onChange(value) {
+    onChange(categoryId) {
       let categoryURL;
 
-      if (value === ALL_CATEGORIES_ID) {
+      if (categoryId === ALL_CATEGORIES_ID) {
         categoryURL = this.allCategoriesUrl;
-      } else if (value === NO_CATEGORIES_ID) {
+      } else if (categoryId === NO_CATEGORIES_ID) {
         categoryURL = this.noCategoriesUrl;
       } else {
-        const categoryId = parseInt(value, 10);
-        const category = Category.findById(categoryId);
-        const slug = Discourse.Category.slugFor(category);
-        categoryURL = `/c/${slug}`;
+        const category = Category.findById(parseInt(categoryId, 10));
+        categoryURL = category.url;
       }
 
       DiscourseURL.routeToUrl(categoryURL);

test/javascripts/components/select-kit/category-drop-test.js.es6

@@ -1,3 +1,4 @@
+import DiscourseURL from "discourse/lib/url";
 import Category from "discourse/models/category";
 import componentTest from "helpers/component-test";
 import { testSelectKitModule } from "./select-kit-test-helper";
@@ -335,3 +336,22 @@ componentTest(
     }
   }
 );
+
+componentTest("category url", {
+  template: template(),
+
+  beforeEach() {
+    initCategoriesWithParentCategory(this);
+    sandbox.stub(DiscourseURL, "routeTo");
+  },
+
+  async test(assert) {
+    await this.subject.expand();
+    await this.subject.selectRowByValue(26);
+
+    assert.ok(
+      DiscourseURL.routeTo.calledWith("/c/feature/spec/26"),
+      "it builds a correct URL"
+    );
+  }
+});