filter/subjecttag: account for missing Subject: header

This is a high indicator of spam (but out-of-scope for this
particular module) but sometimes it is not, and people
legitimately forget to set a Subject: header at all.

diff --git a/lib/PublicInbox/Filter/SubjectTag.pm b/lib/PublicInbox/Filter/SubjectTag.pm
index 1d2814255f9bbe6611186b3a99353ebe268fe26f..7735a94a049f431ccf5bc785cc1315a162ab0fb7 100644 (file)
--- a/lib/PublicInbox/Filter/SubjectTag.pm
+++ b/lib/PublicInbox/Filter/SubjectTag.pm
@@ -19,8 +19,10 @@ sub new {
 sub scrub {
        my ($self, $mime) = @_;
        my $subj = $mime->header('Subject');
-       $subj =~ s/$self->{tag_re}/$1/; # $1 is "Re: "
-       $mime->header_str_set('Subject', $subj);
+       if (defined $subj) {
+               $subj =~ s/$self->{tag_re}/$1/; # $1 is "Re: "
+               $mime->header_str_set('Subject', $subj);
+       }
        $self->ACCEPT($mime);
 }