httpd GzipFilter::zflush error, anyone else seen this?

[Eric Wong]

I'm getting this from inside the PublicInbox::GzipFilter::zflush error:
forward ->close error: Can't call method "flush" on an undefined value at 
../PublicInbox/GzipFilter.pm

I'm not concerned for the error itself, really; it's that I'm
more surprised I haven't seen it in the past.

A backtrace confirms it's triggered by a DS->write failure,
which is common for network servers facing the Internet.

Of course, I haven't paid much attention to syslog in ages and
don't store logs for long; so I just noticed it a few times
since I've started running -netd (and moving away from separate
-httpd/-imapd/-pop3d/-imapd).

Anyways, I think the following should quiet the error message:

diff --git a/lib/PublicInbox/GzipFilter.pm b/lib/PublicInbox/GzipFilter.pm
index e37f1f76..6a25fb8d 100644
--- a/lib/PublicInbox/GzipFilter.pm
+++ b/lib/PublicInbox/GzipFilter.pm
@@ -153,6 +153,7 @@ sub zflush ($;$) {
                $err = $gz->deflate($_[1], $zbuf);
                die "gzip->deflate: $err" if $err != Z_OK;
        }
+       $gz // return; # recursing on DS->write failure
        $err = $gz->flush($zbuf);
        die "gzip->flush: $err" if $err != Z_OK;
        $zbuf;