Fix bug with asset folder view restrictions

In the rare occasion that you have specified several folders in the workspace of an user, and the the first that is found when searched for root-folders (here: id 1) has explicitly set this right to 0, the root folder is also considered to be forbidden even if there are other folders that have the right to be viewed.

This fix searches just for folders that have the right to be viewed, thus passing this to the root folder.
Merge pull request #85 from ThomasKeil/master

Fix bug with asset folder view restrictions