Fix for Bug 6955, Toolbar on reading history broken

Fix for Bug 6955, Toolbar on reading history broken

Table sorter script causes error if there is no <tbody> to sort.
JS errors cause the YUI toolbar js to abort, causing the problem
observed. When there are no results the whole table should be
omitted and a message displayed in its place.

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
To test:
- check toolbar on top of patron reading history with no entries
- check toolbar on top of patron reading history after a few checkouts

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>