SceneInfo optional values

[ricklupton]

This commit (Seb-sti1@ecd56a0) makes the background_visible, root_document_visible and paper_size on the SceneInfo optional

I had some files where the whole SceneInfo was only containing the current_layer property

UnreadableBlock(extra_data=b'',
                error='Bad tag type 0x0 at position 144',
                data=b'\x1c\x06\x00\x00\x00\x1f\x00\x00/\x00\x00',
                info=MainBlockInfo(offset=132,
                                   size=11,
                                   extra_data=b'',
                                   block_type=13,
                                   min_version=0,
                                   current_version=1))

Originally posted by @Seb-sti1 in #34 (comment)

[ricklupton]

Do you have the JSON version of this file? I wonder if it shows a default value for the bool for these. It would be simpler if they were still LwwValue[bool] with a default value for the bool, rather than Optional[LwwValue[bool]]

[Seb-sti1]

I don't think I have a json file for this one, because to get one I think I have to update the file and if I do then all the properties will be added to the file... Although, I'll check and keep you posted, hopefully by the end of the week