str_replace(): Passing null to parameter #3 ($subject) of type array|string is deprecated

line #     FECES_ERROR_HANDLER('8192','str_replace(): Passing null to parameter #3 ($subject) of type array|string is deprecated','/home/puke7/botb/whats/group/group_thread_class.php','24');

line #24     str_replace(array,'_','');
/home/puke7/botb/whats/group/group_thread_class.php

line #191     group_thread::Pop('19681');
/home/puke7/botb/kernel/_STACKMEM.php

line #181     STACK::FetchObject('group_thread','19681');
/home/puke7/botb/kernel/_STACKMEM.php

line #37     STACK::Fetch('group_thread','19681');
/home/puke7/botb/whats/group/group.php

line #93     require('/home/puke7/botb/whats/group/group.php');
/home/puke7/botb/whats/ajax/ajax_class.php

line #79     ajax::inHouse('/group/AjaxGroupThread/19681/battle/4030/');
/home/puke7/botb/whats/group/group_class.php

line #76     group::ReturnThread('19681','battle','4030');
/home/puke7/botb/whats/battle/battle.php

line #93     require('/home/puke7/botb/whats/battle/battle.php');
/home/puke7/botb/whats/ajax/ajax_class.php

line #160     ajax::inHouse('/battle/AjaxMainScreen/4030/kleeder’s OHB Advent Calendar 2018 - Day 23/');
/home/puke7/botb/whats/arena/arena.php

line #30     require_once('/home/puke7/botb/whats/arena/arena.php');
/home/puke7/botb/_FECES.php