Fix brace layer parsing to force int where there may be strings

[jpt]

I was running into this error while converting a file that uses brace layers:

    brace_layers.sort(key=lambda x: tuple(x.location.values()))
TypeError: '<' not supported between instances of 'str' and 'int'

The issue was that my Glyphs file had some integers in its brace layer axis locations, along with some strings. I'm not sure how or why this divergence occurred, but I think it would make sense to force an int for these values.

[anthrotype]

i'm not sure the fix is correct. Can you provide a reproducer?

[jpt]

I'll work on putting together a minimal file that can reproduce this, thanks for looking into it

[bramstein]

For what it is worth: we also ran into this issue with one of our families. It seems the most recent (unreleased) Glyphs version 3.2 automatically fixes this upon saving.