[-] MO : fixed Notice message when save config

ON PS 1.6.0.9 there is a notice when trying to save the configuration :
Notice à la ligne 281 du fichier /var/www/html/projets/stmichel/www/modules/socolissimo/socolissimo.php
[8] Undefined property: Socolissimo::$_html
Merge pull request #2 from MJ-Aristote/patch-1

[-] MO : fixed Notice message when save config