fix(backend): handle undefined array keys username and password

Author: Baraka24

modules/imap/handler_modules.php

@@ -559,7 +559,9 @@ public function process() {
                     } else {
                         $folder = hex2bin($parts[2]);
                     }
-                    
+
+                    $details['password'] =  "";
+                    $details['username'] = $details['user'];
                     $mailbox = Hm_IMAP_List::get_mailbox_without_connection($details);
                     $label = $mailbox->get_folder_name($folder);
                     if(!$label) {