Hidden sheets unhide when loading and saving

[JanMarvin]

• Tab formatting: hidden tabs reappear upon loading and saving the workbook.

Originally posted by @mendy-friedman in #207 (comment)

[JanMarvin]

Pre saving: ColorTabs3.xlsx

After saving: test3.xlsx

[JanMarvin]

From workbook.xml. The hidden argument somehow got lost and should be re-assigned.

pre saving:

<sheets>
    <sheet name="Nums" sheetId="1" r:id="rId1"/>
    <sheet name="Chars" sheetId="2" r:id="rId2"/>
    <sheet name="hidden" sheetId="3" state="hidden" r:id="rId3"/>
</sheets>

post saving:

<sheets>
    <sheet name="Nums" sheetId="1" state="visible" r:id="rId1"/>
    <sheet name="Chars" sheetId="2" state="visible" r:id="rId2"/>
    <sheet name="hidden" sheetId="3" state="visible" r:id="rId3"/>
</sheets>

[JanMarvin]

Seems like something is lost when reading. I'm leaving this for now, if someone is willing to pick this up or fixes it, be my guest :)