for Admin/ tabs..in update modes, only ruled elements can be updated and not the other elements

Link : http://192.168.2.9/drupal/civicrm/admin/locationType

Steps :
1) Click on the link "New Location type"
2) For new location type, enter only Name(say the name be "Test Location").
3) hit "Save"
4) now click on the link "Edit" for "Test Location"
5) (as no description is entered for this location type before..)Enter description for this location type.
6) hit "Save"

Current Behaviour :
Message is displayed that "Name already exists in the Database"

Expected Behaviour:
as mode id update, one can update all the elements of the form even if the elements for which rules are applied, are not updated..
(like in this case..as no description for this location type..one should be allowed to add that any later moment...one may also want to change the location description after some time, keeping the name of location same..)