Bug 7926: Acq search results show empty () for orders without basket group

Bug 7926: Acq search results show empty () for orders without basket group

To test:
- search for orders by title or vendor
- make sure some results are attached to a basket group, while others are not
- make sure correct information shows in the basket group column of search results

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
- Fixed merge conflict

Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>