Add guard for options.WorkingDirectory (#893)
Add guard for options.WorkingDirectory (#893)

When testing, workingDirectory can be null. Added a guard
orbitcowboy/MIEngine,Microsoft/MIEngine,orbitcowboy/MIEngine,Microsoft/MIEngine,orbitcowboy/MIEngine,Microsoft/MIEngine,orbitcowboy/MIEngine,Microsoft/MIEngine