(web) fix add-by-URL regression in the nightlies

git-svn-id: svn://svn.transmissionbt.com/Transmission/trunk@14061 f4695dd4-2c0a-0410-b89c-da849a56a58e
(qt) if freespace can't be determined, don't show it in the label. reported by rb07 in https://trac.transmissionbt.com/ticket/4076#comment:45

git-svn-id: svn://svn.transmissionbt.com/Transmission/trunk@14062 f4695dd4-2c0a-0410-b89c-da849a56a58e
(qt) increase the freespace-label update interval from 5 seconds to 15 seconds

git-svn-id: svn://svn.transmissionbt.com/Transmission/trunk@14063 f4695dd4-2c0a-0410-b89c-da849a56a58e