Saving permissions filtered by role crashes upon submission

[bugfolder]

Testing version 1.0.4 with Backdrop 1.23.0. To reproduce:

• Go to the Permissions page at admin/config/people/permissions.
• Filter to a single role (e.g., Editor).
• Click "Save Permissions" (you don't need to change anything).

Result is this error:

Argument 2 passed to user_role_change_permissions() must be of the type array, null given, called in /mysite/core/modules/user/user.admin.inc on line 494

The relevant code is:

function user_admin_permissions_submit($form, &$form_state) {
  foreach ($form_state['values']['roles'] as $role_name => $role) {
    user_role_change_permissions($role->name, $form_state['values'][$role->name]);
  }

The problem is that although we've filtered only to the Editor role, $form_state['values']['roles'] still contains all roles. But $form_state['values'][$role->name] doesn't have an entry for any of the other roles.

[bugfolder]

PR submitted.

[yorkshire-pudding]

Thanks @bugfolder - Sorry for the delay in responding; I need to adjust my email notification settings.
This PR does fix exactly what it says on the tin and therefore I will merge it. However testing this has made me aware of another UX issue with the module that I will raise separately: #8