protecting against unfinished worker objects after raising of exception and moving non-concurrent task operation code into - (void)main
Merge commit '6ecb1a19205e45ee1b439d6fa27ad7c3f7296c09'

* commit '6ecb1a19205e45ee1b439d6fa27ad7c3f7296c09':
  updating dependencies
  Revert "adding unit test for worker cancellation"