Banshee exception

Fatal errors: => htmlspecialchars(): Passing null to parameter #1 ($string) of type string is deprecated line 72 in /home/hugo/websites/banshee/demo/libraries/banshee/core/xml.php

line 197 in /home/hugo/websites/banshee/demo/public/index.php.

=> Undefined array key "previous_pages" line 119 in /home/hugo/websites/banshee/demo/libraries/banshee/core/page.php