Hypothetical failure point

This exception is not added to the list of uncaught exceptions.  Instead, Whiskey chokes with the following response:

```
$ NODE_PATH=$(pwd)/lib-cov bin/whiskey --coverage --coverage-reporter cli --coverage-file /tmp/hooey --coverage-dir /tmp -t example/test-bdd.js                                                                                                                                                                   /Users/sfalvo/git/whiskey :: Tue Jun 11 11:00:50 PDT 2013
path.existsSync is now called `fs.existsSync`.
/Users/sfalvo/git/whiskey/example/test-bdd.js

Stderr:

/Users/sfalvo/git/whiskey/lib/common.js:537
    test._testObj.finish();
                  ^
TypeError: Cannot call method 'finish' of null
    at TestFile.addUncaughtException (/Users/sfalvo/git/whiskey/lib/common.js:537:19)
    at process.<anonymous> (/Users/sfalvo/git/whiskey/lib/run_test_file.js:106:12)
    at process.EventEmitter.emit (events.js:95:17)
    at process._fatalException (node.js:272:26)

---------------------------------------------------------------------------------
Ran 0 tests in 0.089s

Successes: 0
Failures: 0
Timeouts: 0
Skipped: 0

PASSED

Test Coverage
   +------------------------------------------+----------+------+------+--------+
   | filename                                 | coverage | LOC  | SLOC | missed |
   +------------------------------------------+----------+------+------+--------+
   +------------------------------------------+----------+------+------+--------+
                                              |      NaN |    0 |    0 |      0 |
                                              +----------+------+------+--------+
```