MAGN-4754 Changes to select faces broke old test and changed behavior.

http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-4754

Merges:
- [ ] Revit2015

Reviewers:
- [ ] @Steell 
ViewModel.Model.RunExpression should ideally never throw; Assert.DoesNotThrow should be reserved for cases where we're testing code that is expected to throw under certain circumstances.

This isn't critical, just an observation. I'm worried that sometimes using Assert.DoesNotThrow swallows error that would otherwise help us debug a failing unit test. Use your best judgement here.