use the optional third parameter (defaulted to 0)

The function should have a third parameter, not an issue.

Python version returns the following error:

  File "tests.py", line 8, in <module>
    test.assert_equals(or_arrays([1,0,3],[1,2,3],3),[1,2,3])
TypeError: or_arrays() takes 2 positional arguments but 3 were given