Bug 21027: Fix checkout statistics if 1+ of the fields is not defined

TEST

- Use a patron who hasn't checked out items before
- Set  StatisticsFields to itype|ccode
- Check out some items without location
- Verify that statistics stable shows the correct number of checkouts
- Check out one item with a location or just change one of your checked out items
- Verify the total is still correct
- Change  StatisticsFields to location|itype|ccode
- Verify the total has changed now - it's only 1 (the one with a location)

Apply the patch and try again

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

members/statistics.pl

@@ -198,7 +198,10 @@ sub merge {
         for my $ch ( @r ) {
             $exists = 1;
             for my $cn ( @statistic_column_names ) {
-                if ( $ch->{$cn} and not $ch->{$cn} eq $h->{$cn} ) {
+                if (   ( not defined $ch->{$cn} && defined $h->{$cn} )
+                    || ( defined $ch->{$cn} && not defined $h->{$cn} )
+                    || ( $ch->{$cn} ne $h->{$cn} ) )
+                {
                     $exists = 0;
                     last;
                 }