Code checking if the needle string `$value` is somewhere in the haystack `"\0"` makes no sense for a single byte (if it did, then `strcmp` instead of `strpos` should have been used) and the created exception output implies that it's supposed to check that a string does not contain NULL bytes.
Thus switch the order of arguments passed to `strpos()` to be correct.
```
EXCEPTION: (RuntimeException) strpos(): Non-string needles will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior at [<arcanist>/src/error/PhutilErrorHandler.php:261]
#0 <#2> PhutilErrorHandler::handleError(integer, string, string, integer, array) called at [<arcanist>/src/error/PhutilErrorHandler.php:261]
#1 <#2> strpos(string, integer) called at [<arcanist>/src/utils/PhutilSortVector.php:33]
```
Closes T15755