As the title suggests, the blocked robot avatar stays in world space and never disappears under specific behavior steps until the client terminates.
This is a bug that occurs when viewing the details of an unavailable avatar and then viewing the details of another avatar.
Also it follows the user's main menu objects, I assume because it's the child of the menu.
Reproduction steps:
  1. Open the Avatar menu in MM
  2. Click and see the details of the unavailable avatar
  3. Back to the list and click again on the "ⓘ" button
  4. You'll see the blocked avatar with the other one; it will not disappear until the client terminates.
The video of the reproduction steps is embedded.