Preview Activity - Missing required field check for Subject - CiviCRM 2.1.4

while importing activities in civicrm, if the subject field is not present it dose not give warning in preview step (step 3/4), but it results in error while importing.
here is the problem that describes this case :

• Add an activity of any type manually for any contact - please note "Subject" is a required field.
• Import an activity using the attached csv file .
• The Preview step dose not flag the error for missing subject and when the actual import is done it gives an error message -
  "Sorry. A non-recoverable error has occurred.
  Not enough data to create activity object,
  Return to home page."

both problem & patch for the same is present at :
http://forum.civicrm.org/index.php/topic,6040.msg26546.html#msg26546 .