panic: runtime error: index out of range

[shibukawa]

goroutine 1 [running, locked to thread]:
github.com/shibukawa/nanovgo/fontstashmini.(*Atlas).rectFits(0xc82023ccc0, 0x2a, 0x12, 0x12, 0xffffffffffffffff)
    github.com/shibukawa/nanovgo/fontstashmini/atlas.go:29 +0x14d
github.com/shibukawa/nanovgo/fontstashmini.(*Atlas).addRect(0xc82023ccc0, 0x12, 0x12, 0x1c4, 0x34, 0x0, 0x0)
    github.com/shibukawa/nanovgo/fontstashmini/atlas.go:96 +0x11c
github.com/shibukawa/nanovgo/fontstashmini.(*FontStash).getGlyph(0xc8202387e0, 0xc8201a5d40, 0x2713, 0xc8, 0x0, 0xbf800000)
    github.com/shibukawa/nanovgo/fontstashmini/fontstash_mini.go:454 +0x2d7
github.com/shibukawa/nanovgo/fontstashmini.(*FontStash).TextBoundsOfRunes(0xc8202387e0, 0x439a80c442380000, 0xc8212e3020, 0x1, 0x2, 0x0, 0x0, 0x0, 0x0)
    github.com/shibukawa/nanovgo/fontstashmini/fontstash_mini.go:285 +0x345
github.com/shibukawa/nanovgo/fontstashmini.(*FontStash).TextIterForRunes(0xc8202387e0, 0x4397000042380000, 0xc8212e3020, 0x1, 0x2, 0x8)
    github.com/shibukawa/nanovgo/fontstashmini/fontstash_mini.go:338 +0x55b
github.com/shibukawa/nanovgo.(*Context).TextRune(0xc8201b4500, 0x4397000042380000, 0xc8212e3020, 0x1, 0x2, 0x2)
    github.com/shibukawa/nanovgo/nanovgo.go:890 +0x409
github.com/shibukawa/nanovgo.(*Context).Text(0xc8201b4500, 0x4397000042380000, 0xc82139d3d0, 0x3, 0xc82139d3d0)
    github.com/shibukawa/nanovgo/nanovgo.go:869 +0x8e
github.com/shibukawa/nanogui%2ego.(*CheckBox).Draw(0xc8202240d0, 0x5ec1e08, 0xc8202240d0, 0xc8201b4500)
    github.com/shibukawa/nanogui.go/checkbox.go:125 +0x9a4
github.com/shibukawa/nanogui%2ego.(*WidgetImplement).Draw(0xc8201be8c0, 0x5ec09c8, 0xc8201be8c0, 0xc8201b4500)