Passing null instead of a string or array to str_replace() deprecated since PHP 8.1.
Thus do not create a title array with a null entry in DivinerFindController when there is no $query_text, later to be read via $this->titles in DivinerAtomRef.
ERROR 8192: str_replace(): Passing null to parameter #3 ($subject) of type array|string is deprecated at [/var/www/html/phorge/phorge/src/applications/diviner/atom/DivinerAtomRef.php:205] #0 str_replace(string, string, NULL) called at [<phorge>/src/applications/diviner/atom/DivinerAtomRef.php:205] #1 DivinerAtomRef::normalizeTitleString(NULL) called at [<phorge>/src/applications/diviner/query/DivinerAtomQuery.php:344]
Credits to valerio.bozzolan for finding the right spot in the code.
Closes T15911