fix: because version.start_date returns the earliest start date of the associated issues if no own start_date is set, we have to read the attribute :start_date directly when making executing the sprint_start_date/start_date migration

db/migrate/20110513130147_remove_sprint_start_date.rb

@@ -8,12 +8,12 @@ class RemoveSprintStartDate < ActiveRecord::Migration
 
     Version.transaction do
       Version.all.each do |version|
-        if version.sprint_start_date.present? and version.start_date.present? and
-           version.sprint_start_date != version.start_date
+        if version.sprint_start_date.present? and version.read_attribute(:start_date).present? and
+           version.sprint_start_date != version.read_attribute(:start_date)
 
           raise "Version #{version.id} has a start date and a sprint start date! Migrations were not executed in the correct order"
 
-        elsif version.sprint_start_date.present? and version.start_date.blank?
+        elsif version.sprint_start_date.present? and version.read_attribute(:start_date).blank?
           puts "Copying sprint_start_date to start_date for Sprint #{version.id} - #{version.name.inspect}"
           version.start_date = version.sprint_start_date
           version.save!