The controller threw an error when a start date was not defined because it was

trying to format the string.  In the generate method, we already have logic to
return nil if the start date is not defined, so I added a check in the fetch
method to return nil if the generate method exited with a nil status.

app/models/backlog_chart_data.rb

@@ -28,8 +28,10 @@ class BacklogChartData < ActiveRecord::Base
 
   def self.fetch(options = {})
     backlog = Backlog.find(options[:backlog_id])
-    generate backlog
-    end_date = backlog.end_date || 30.days.from_now.to_date
+    if generate(backlog).nil?
+        return nil
+    end
+    end_date = backlog.end_date
     data = find_all_by_backlog_id backlog.id, :conditions => ["created_at>=? AND created_at<=?", backlog.start_date.to_formatted_s(:db), end_date.to_formatted_s(:db)], :order => "created_at ASC"
 
     return nil if data.nil? || data.length==0