Bug 9923: (MT #11060) actual cost not getting populated

Bug 9923: (MT #11060) actual cost not getting populated

The patch 7129 introduces a bug if the unitprice is 0.0000.
Instead of showing in this case the 'ecost' if there is not 'unitprice',
it shows 0.00 and the 'Actual cost' must be manually entered. The line:
if ( @$results[0]->{'unitprice'} == 0 ) {
    @$results[0]->{'unitprice'} = '';

was wrote in this perspective.
But sprintf ( "%.2f", with '' or 0 or any string will return 0.00
and then, in the .tt 'unitprice' exists so we have the bad result.

Signed-off-by: Mathieu Saby <mathieu.saby@univ-rennes2.fr>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>