Add default order for admin budget investments list

When there's no sorting option selected, by default it orders the investment list by supports and, for those with the same number of supports, by ID.

app/controllers/admin/budget_investments_controller.rb

@@ -77,7 +77,7 @@ class Admin::BudgetInvestmentsController < Admin::BaseController
 
     def load_investments
       @investments = Budget::Investment.scoped_filter(params, @current_filter)
-      @investments = @investments.order_filter(params[:sort_by]) if params[:sort_by].present?
+                                       .order_filter(params[:sort_by])
       @investments = @investments.page(params[:page]) unless request.format.csv?
     end
 

app/models/budget/investment.rb

@@ -142,6 +142,8 @@ class Budget
     def self.order_filter(sorting_param)
       if sorting_param.present? && SORTING_OPTIONS.include?(sorting_param)
         send("sort_by_#{sorting_param}")
+      else
+        order(cached_votes_up: :desc).order(id: :desc)
       end
     end
 

spec/features/admin/budget_investments_spec.rb

@@ -603,6 +603,16 @@ feature 'Admin budget investments' do
       create(:budget_investment, title: 'C Third Investment', cached_votes_up: 10, budget: budget)
     end
 
+    scenario "Default sorting" do
+      create(:budget_investment, title: 'D Fourth Investment', cached_votes_up: 50, budget: budget)
+
+      visit admin_budget_budget_investments_path(budget)
+
+      expect('D Fourth Investment').to appear_before('B First Investment')
+      expect('D Fourth Investment').to appear_before('A Second Investment')
+      expect('A Second Investment').to appear_before('C Third Investment')
+    end
+
     scenario 'Sort by ID' do
       visit admin_budget_budget_investments_path(budget, sort_by: 'id')