Bug 10032: Improve GUI when uncertain price prevents closing the basket

Bug 10032: Improve GUI when uncertain price prevents closing the basket

Added disabled "Close this basket" button when uncertain
prices are present.
Note that whilst this has a "title" attribute, there is no tooltip
shown because JQueryUI disabled buttons don't get DOM events.

https://bugs.koha-community.org/show_bug.cgi?id=10032

Signed-off-by: Charlotte Cordwell <charlotte.cordwell123@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>