[imapsync] patch for 1.267: avoid undefined var warnings on append failure when subject is undefined

[Phil Lobbes <plobbes at zimbra dot com>]

When an APPEND fails, imapsync may cause an undefined var warning IF the subject of a message is undefined (which is rare, but not impossible):

This patch avoids that minor annoyance in the STDERR output.

Phil
-- 
Phil Lobbes
Zimbra, a Yahoo! company

$ diff -u imapsync.ORIG imapsync
--- imapsync.ORIG       2009-02-19 17:54:15.000000000 -0500
+++ imapsync    2009-02-19 17:55:18.000000000 -0500
@@ -1529,6 +1529,7 @@
                                        $new_id = $to->append_string($t_fold,$string, $flags_f, $d);
                                }
                                unless($new_id){
+                                       no warnings 'uninitialized';
                                        warn "Couldn't append msg #$f_msg (Subject:[".
                                          $from->subject($f_msg)."]) to folder $t_fold: ",
                                          $to->LastError, "\n";