Passing null as an input string to explode() is deprecated in PHP 8.
Thus first check via phutil_nonempty_string() that the input string is not null.
Note: this may highlight other absurd input values that might be worth correcting
instead of just ignoring. If phutil_nonempty_string() throws an exception in your
instance, report it to Phorge to evaluate and fix that specific corner case.
Closes T15361
