Solved the error with NaN in the popup for websites with no time spent

    When a blacklisted website was not accessed, in the pop-up the
    NaN was displayed. This was due to the fact that the pop-up data
    should be an array but a 0 value was returned.

    Now we check if we have an entry for today and if not we create
    an array with value 0 which can be parsed by the functions in
    pop-up.

    In pop-up, the value 0.00 is displayed each time a balcklisted site
    is not accessed at all.