When dumping thread info, only include the filename and line if we actually know what file! (Prevents use of NULL).
When dumping thread info, only include the filename and line if we actually
know what file! (Prevents use of NULL).

MFC after:	1 day
Reviewed by:	deischen

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