Merge pull request #669 in ZP/z-push from...

Merge pull request #669 in ZP/z-push from bugfix/ZP-1377-undefined-index-warnings-in-imap-backend to develop

* commit '69c08ccd':
  ZP-1377 Fix undefined index warnings in imap backend.

src/backend/imap/imap.php

@@ -205,8 +205,12 @@ class BackendIMAP extends BackendDiff implements ISearchProvider {
             ZLog::Write(LOGLEVEL_DEBUG, sprintf("BackendIMAP->SendMail(): To defined: %s", $toaddr));
         }
 
-        $message->headers["to"] = Utils::CheckAndFixEncodingInHeadersOfSentMail($Mail_RFC822->parseAddressList($message->headers["to"]));
-        $message->headers["cc"] = Utils::CheckAndFixEncodingInHeadersOfSentMail($Mail_RFC822->parseAddressList($message->headers["cc"]));
+        if (isset($message->headers["to"])) {
+            $message->headers["to"] = Utils::CheckAndFixEncodingInHeadersOfSentMail($Mail_RFC822->parseAddressList($message->headers["to"]));
+        }
+        if (isset($message->headers["cc"])) {
+            $message->headers["cc"] = Utils::CheckAndFixEncodingInHeadersOfSentMail($Mail_RFC822->parseAddressList($message->headers["cc"]));
+        }
 
         unset($Mail_RFC822);