Setting MediaEntryStatus in MediaEntryList to allow null values

[MikiDylewski]

Reason for the PR:
When user adds custom list it's status becomes null, or rather is not in the enum. Because of that #GetUserEntryCollectionAsync() throws and error that it cannot be parsed.

To test that can be null click here

To reproduce simply:

await _client.GetUserEntryCollectionAsync(165049, MediaType.Anime, new AniPaginationOptions(1, 500))

No tests were written as no core changes were made

[dentolos19]

Thanks for the fix! Will release this as soon as possible.