Silently return NULL from devclass_get_device if dc == NULL. The caller should be handling NULL returns already.
Silently return NULL from devclass_get_device if dc == NULL. The caller
should be handling NULL returns already.

Submitted by: Andrew Gallatin <gallatin@cs.duke.edu>

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase