Make sure every wrapper that takes a pointer to a driver's object is protected against NULLs

[manenko]

Some wrappers should fail when given a NULL-pointer to an object to wrap. In these cases, a NULL-pointer is often a programmer's error, so it is probably better to panic instead of returning an error.

Returning an error makes the API less convenient to use. On the other hand, it allows the crate's clients to perform a graceful shutdown.