[FIX] feature memcache: validate access instance of memcache object of null.
Tiki as a builtin feature to workwith memcached, but there is few with the feature while activated, in case you did not provide the memcache server address, it crach your Tiki instance. So the observation is missing validation after migration of tiki to php8, whitch is very strict.
Edited by Boss Ibrahim Mussa Gregoire