FIX: Don't error out on nested categories index page param (#29273)

We're expecting the page param to be something that neatly coerces into an integer. If we receive something like a nested parameter, this will blow up. (I'm sure there are other examples as well.)

This commit falls back to a page value of 1 if the coercion fails.

app/controllers/categories_controller.rb

@@ -620,7 +620,7 @@ class CategoriesController < ApplicationController
       include_topics: include_topics,
       include_subcategories: include_subcategories,
       tag: params[:tag],
-      page: params[:page].to_i,
+      page: params[:page].try(:to_i) || 1,
     }
 
     @category_list = CategoryList.new(guardian, category_options)