Fixed null pointer panic for misconfigured master ports.
Fixed null pointer panic for misconfigured master ports.

PR:		i386/10273
Submitted by:	Stephen Kiernan <sab@yin.vegamuse.org>

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