Clef glyphs will disappear if placed on a specific spot in the page

[thesoundbyle]

The issue only has been observed to affect clef glyphs.

[annamorphism]

Looks like the clef disappears whenever it is put on "line 0" of the staff. (One can put it on a negative line, but it invalidates the file.) The information for the notes shows up as if there is a clef on "line 0", but it doesn't display!

[annamorphism]

Update: it seems like what happens is that putting the clef on line 0 (i.e. giving it a line attribute of 0) just deletes the line attribute altogether, and so the clefs don't show up anywhere (but do manage to relabel the notes before they fly away!). Seems like "line 0" should be handled like negative lines in terms of how it renders the clef and invalidates the file.