Token arithmetic operations on glyph name that has a hyphen

[sovichet (Sovichet Tep)]

I can access the properties of a glyph (with a hyphen in its name) just fine, but it will show errors when I perform the arithmetic operations on it.

${zero-myanmar:width} is fine, but ${zero-myanmar:width/2} is not.

[GeorgSeifert]

Thanks for finding this. I fixed it.