view: allow for missing In-Reply-To mapping

Because buggy mail clients exist and generate invalid
In-Reply-To headers we cannot handle across the board...

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/PublicInbox/View.pm b/lib/PublicInbox/View.pm
index ed3c96e8..373545a2 100644
--- a/lib/PublicInbox/View.pm
+++ b/lib/PublicInbox/View.pm
@@ -208,8 +208,8 @@ sub _th_index_lite {
         my $nr_s = 0;
         my $level = $map->[4];
         my $idx = $map->[3];
-        if (defined $irt) {
-                my $irt_map = $mapping->{$irt};
+        my $irt_map = $mapping->{$irt} if defined $irt;
+        if (defined $irt_map) {
                 my $siblings = $irt_map->[0];
                 $nr_s = scalar(@$siblings) - 1;
                 $rv .= $pad . $irt_map->[1];