Remove bottleneck making claims page unuseable

Remove bottleneck making claims page unuseable

While the idea of showing the number of late serials against the
vendor name was nice it does not scale and on large sites selecting claims
was just timing out. Improved the speed of the initial query but have removed
the big query for each user just to get a count.
Check for 0000-00-00 dates so that C4::Dates does not log error
Removed a variable that was never set and the bit of template used
if the impossible happened