Parts dialog shows no part names after parts are generated

More information: if you then save and reload the score, then when you open the Parts dialog, the list at left is at least populated with the correct names. However, selecting one of them does not allow you to edit the part in the widgets at right.

This all used to work, and I can guess the change relates to this:

https://github.com/musescore/MuseScore/commit/17d7ac245026b70b887ba0007…

but I'm not understanding it well enough to fix.

What I can see so far is that somewhere around here would be a good place to set the title of the part, by moving the call to nscore()->setName(e->title()) up here:

https://github.com/musescore/MuseScore/blob/17d7ac245026b70b887ba00072f…

That allows the part names to be populated next time you open the dialog, but you still see the same effect as after save/load: the part titles are visible, but clicking them does not actually allow you to edit the part with the controls at right. That's because right here, idx keeps coming back -1:

https://github.com/musescore/MuseScore/blob/17d7ac245026b70b887ba00072f…

I guess somehow the copying of things is not working right, but I don't get how it is supposed to work. Hopefully someone else can take it from here.

The part names show up now, so at least deleting parts is easier. But you still can't edit parts. Clicking a part is supposed to enable the controls on the right to allow you to add & remove staves. Looks like maybe this is by design, though:

https://github.com/musescore/MuseScore/blob/17d7ac245026b70b887ba00072f…

Disables the controls if the part has already been generated it seems. Odd, I would have sworn this used to work.