Removing all the dashlets from the dashboard leads to E_NOTICE
You don't see it on the screen but it's in e.g. drupal watchdog.
Notice: Undefined index: columns in CRM_Contact_Page_AJAX::dashboard() (line 509 of .../CRM/Contact/Page/AJAX.php)
It only seems to create the notice at the point when you remove the last dashlet. Subsequent visits to a blank dashboard are fine. You can reproduce it again by adding a dashlet to the blank dashboard and then removing it.