Fix ALDeviceList::GetDeviceVersion incorrect check of valid pointer.

```
 void ALDeviceList::GetDeviceVersion(int index, int *major, int *minor)
 {
 	if (index < GetNumDevices()) {
		if (*major) // not check if it's pointer is valid, and can deferrencing a NULL pointer.
                   *major = vDeviceInfo[index].iMajorVersion;
       ...
}