Allow user to change the age of a person if they're not actually under 16 without being blocked

app/models/derived_variables/sales_log_variables.rb

@@ -160,6 +160,8 @@ private
     (start_index..6).each do |idx|
       if age_under_16?(idx)
         self["ecstat#{idx}"] = 9
+      elsif self["ecstat#{idx}"] == 9
+        self["ecstat#{idx}"] = nil
       end
     end
   end