Additional exception when there is an exception in tests

[mitar]

If tests throw an exception, then in the console there is also another exception:

Exception from Tracker afterFlush function:
Error: Can't call Tracker.flush while flushing
    at Object.Tracker._runFlush (tracker.js:432)
    at Object.Tracker.flush (tracker.js:412)
    at driver.js:48
    at Tinytest._runTestsEverywhere.maybeDone (tinytest_client.js:25)
    at tinytest_client.js:36
    at _.extend.run.runNext (tinytest.js:592)
    at tinytest.js:572
    at tinytest.js:519
    at null.onException (tinytest.js:401)
    at _.extend.exception (tinytest.js:104)