fix: return 0 if no process found

lib/Site/PSVar.pm

@@ -63,7 +63,13 @@ sub handler {
     my @values = split(/\n/, $output);
     my $title = shift @values;
     my @sorted = sort @values;
-    my $value = ( $aggr eq 'max' ) ? pop @sorted : shift @sorted;
+    my $value;
+    if (scalar @value) {
+       $value = ( $aggr eq 'max' ) ? pop @sorted : shift @sorted;
+    }
+    else {
+       $value = 0
+    }
 
 
     return {