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 
I always wrap a call to RunExpression() in this assertion because, although it shouldn't ever throw an exception, if it does, the exception's trace will be shown in the test result and the test will be marked as a failure instead of an error.