fixes of obvious code mistakes

[DamirAinullin]

fixes of some simple obvious code mistakes and warnings.

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[mjbvz]

This changes the behavior and some analyzers will complain about comparing to string.Empty directly. Is there a specific reason for this change?

[DamirAinullin]

We use WorkingDirectory at the line 152, before check it for null. So I can suppose that check is not needed. Maybe NullReferenceException is possible at the line 152. Maybe we should check it for null before using.

[mjbvz]

Thanks for the fixes. Just one small comment to take a look at before we merge this in.

What tool did you use to find these?

[DamirAinullin]

Thanks for positive response. I just try to help your project. I use static analyser PVS-Studio. It is a wonderful tool.

[mjbvz]

Thanks for details and thanks again for finding these. LGTM, merging this in now.