[Neon staging] Changing a head shape only works after inputting another glyph

[JoyfulGen]

If you select a glyph using the neume component selector and change its head shape, you get a notification that the shape was changed, but nothing happens. If you then input any other glyph, the shape suddenly changes.

Demo:

staging.head.shape.mov

A fun fact is that Neon "remembers" all the shape changes. So if you change many note heads in a row, nothing happens, but as soon as you input a new glyph all of the changes happen at once!