Combobox changed resets wavetable position on startup

[EricGeorge]

It makes sense to reset wavetable position when the wavetable changes (in response to a combobox change). But we are getting the combobox change on startup - maybe in response to a plugin state being restored. However, that overwrites any wavetable position that was stored.

Also - it seems that the wavetable in the combobox doesn't restore anyways.

The code is pretty fragile when restoring plugin state.