Error message: Deprecated Functionality: strpos(): Passing null to parameter #1 ($haystack)

Question

Since a upgrade to PHP 8.1 from 7.4 we are getting this error in an application:

Error message: Deprecated Functionality: strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated in /Model/Plugin/Order.php on line 33

Line 33 is a IF-statement

33. if (strpos($orderStatus, '_') !== false) {
34. do stuff...
35. }

Is it possible to change it in someway to be able to handle null values?

Thanks,