Order Budget headings by id when calculating heading stats

app/models/budget/stats.rb

@@ -129,7 +129,7 @@ class Budget
       def headings
         stats_cache("headings") do
           groups = Hash.new(0)
-          @budget.headings.each do |heading|
+          @budget.headings.order("id ASC").each do |heading|
             groups[heading.id] = Hash.new(0).merge(calculate_heading_totals(heading))
           end