Description of problem:
when one user/group-permission entry in Permissions tab is selected, user is able to remove it but when he selects another entry to remove them at once, "remove" button goes inactive.

Version-Release number of selected component (if applicable):
3.0.3

How reproducible:
always

Steps to Reproduce:
1. have an object where there are more than two entries that user can remove
2. select both entries
3.
  
Actual results:
"remove" button is inactive, user must remove entries one-by-one

Expected results:
user can remove multiple permission entries at once

Additional info: