Add ErrNilDialFunc and return it from DialWithCustomDialer. We add it here instead of the customDialer method since it only needs to be checked once, not every time a dial attempt is made, and it is similiar to other checks made by Dial* funcs
Add ErrNilDialFunc and return it from DialWithCustomDialer. We add it here instead of the customDialer method since it only needs to be checked once, not every time a dial attempt is made, and it is similiar to other checks made by Dial* funcs

RackSec/srslog,RackSec/srslog,RackSec/srslog