I hope this time, it's really an easy one :)
Someone the substring_index replacement function for sqlite does get called with empty string during the upgrade process and it doesn't like this because of this line:
$end = strpos($string, $delimiter, $end + 1);
In case of an empty string, this translates to strpos('', '/', 1) and then strpos() complains that it offset is bigger than the string length.
Patch checks if $string is empty and returns an empty string then.
Hm, evil patch... :)