FIX: Category drop shows undefined (#11090)

After 5fc239b535, the category dropdown
was showing "undefined" for the "all-categories" and "no-categories"
messages. This commit introduces a check to run the HTML parser only if
we're dealing with a real category, which fixes the above issue.

app/assets/javascripts/select-kit/addon/components/category-row.js

@@ -39,9 +39,11 @@ export default SelectKitRowComponent.extend({
     "description",
     "categoryName",
     function () {
-      return htmlToText(
-        this.descriptionText || this.description || this.categoryName
-      );
+      if (this.category) {
+        return htmlToText(
+          this.descriptionText || this.description || this.categoryName
+        );
+      }
     }
   ),