Introduced a helper function to improve the readability of tests in the libtorrent component. This function converts bitarray representations into base64, making it easier to understand and verify the expected results. The changes are applied in tests that check if correct pieces bitmask is returned when requested.

Adjusted the method for generating a base64 encoded bitmask of downloaded pieces. Now, it includes a try-except block to handle potential ValueError exceptions that could occur if the list of pieces is corrupted. This change ensures that an empty string is returned instead of allowing the exception to propagate. Additionally, a corresponding test case has been added to verify this new behavior when dealing with corrupted piece lists.