Overlapping paths rendered incorrectly

[WesleyAC]

The @ symbol from the Feather icon set has some overlapping paths, which fontcustom renders incorrectly:

The overlap is treated as negative space when it shouldn't be.

It seems like fontcustom is unmaintained, so I don't expect this to be fixed, but for future travelers: grunt-webfont is the only thing I've found that correctly handles this case.