index: avoid setting NPROC to undef

This quiets a warning inside Spawn.pm

diff --git a/script/public-inbox-index b/script/public-inbox-index
index db7ebbab6421ec2cc1b849e4259b2ac82d6d745b..2a7a524b34abee1765c3adc9288b64cf29dac78e 100755 (executable)
--- a/script/public-inbox-index
+++ b/script/public-inbox-index
@@ -101,7 +101,7 @@ sub index_dir {
                eval { require PublicInbox::V2Writable };
                die "v2 requirements not met: $@\n" if $@;
                my $v2w = eval {
-                       local $ENV{NPROC} = $jobs if $jobs;
+                       $jobs and local $ENV{NPROC} = $jobs;
                        PublicInbox::V2Writable->new($repo);
                };
                if (defined $jobs) {