commit 97dc6583c41605beda7eced3ba05fc578cfd6111
Author: Scott Shambarger <devel@shambarger.net>
Date:   Wed May 29 20:07:18 2019 -0700

    Fix Issue #56: Undefined Indices in Logs

    Add ssl_mode and force_caps to connection params, and correctly handle
    AUTHENTICATE PLAIN in putLineC to reduce warnings in logs.

    Signed-off-by: Scott Shambarger <devel@shambarger.net>

diff --git a/lib/imap/imap_rcube.php b/lib/imap/imap_rcube.php
index f5b5b79..ceec1e5 100644
--- a/lib/imap/imap_rcube.php
+++ b/lib/imap/imap_rcube.php
@@ -146,7 +146,7 @@ class imap_rcube
         $res = 0;
         if ($parts = preg_split('/(\{[0-9]+\}\r\n)/m', $string, -1, PREG_SPLIT_DELIM_CAPTURE)) {
             for ($i=0, $cnt=count($parts); $i<$cnt; $i++) {
-                if (preg_match('/^\{([0-9]+)\}\r\n$/', $parts[$i+1], $matches)) {
+                if (isset($parts[$i+1]) && preg_match('/^\{([0-9]+)\}\r\n$/', $parts[$i+1], $matches)) {
                     // LITERAL+ support
                     if ($this->prefs['literal+']) {
                         $parts[$i+1] = sprintf("{%d+}\r\n", $matches[1]);