panic: runtime error: invalid memory address or nil pointer dereference

[kornel661]

The package compiles &installs without errors but examples/minimal.go terminates with an error (no GUI is shown):

$ go build -ldflags '-r ../lib' minimal.go
$ ./minimal
go-ui 0.1.1
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x4 pc=0x34d4b52e81]

goroutine 1 [syscall]:
github.com/visualfc/go-ui/ui._Cfunc_drv(0x900000007, 0xf84008e0c0)
github.com/visualfc/go-ui/ui/_obj/_cgo_defun.c:42 +0x34
github.com/visualfc/go-ui/ui._drv_ch(0x900000007, 0xf840071ea0, 0xf84008e0b8, 0x0, 0x0, ...)
github.com/visualfc/go-ui/ui/_obj/cdrv.cgo1.go:236 +0xc1
github.com/visualfc/go-ui/ui.(_Widget).SetVisible(0xf840071ea0, 0x1, 0x400dc4, 0xf840071ea0)
/home/kornel/dokumenty/programowanie/golang/test1/src/github.com/visualfc/go-ui/ui/uiobjs.go:2343 +0xaf
github.com/visualfc/go-ui/ui.(_Widget).Show(0xf840071ea0, 0xc80000012c)
/home/kornel/dokumenty/programowanie/golang/test1/src/github.com/visualfc/go-ui/ui/uiobjs.go:2623 +0x2a
main._func_001()
/home/kornel/dokumenty/programowanie/golang/test1/src/github.com/visualfc/go-ui/examples/minimal.go:15 +0xb2
github.com/visualfc/go-ui/ui.drv_appmain()
github.com/visualfc/go-ui/ui/_obj/cdrv.cgo1.go:292 +0x5c
----- stack segment boundary -----
github.com/visualfc/go-ui/ui._Cfunc_drv(0x100000001, 0x0)
github.com/visualfc/go-ui/ui/_obj/_cgo_defun.c:42 +0x34
github.com/visualfc/go-ui/ui._drv(0x100000001, 0x621828, 0xf84008e060, 0x0, 0x0, ...)
github.com/visualfc/go-ui/ui/_obj/cdrv.cgo1.go:228 +0x88
github.com/visualfc/go-ui/ui.(*app).AppMain(0x621828, 0x0, 0x400cc4, 0x400d12)
/home/kornel/dokumenty/programowanie/golang/test1/src/github.com/visualfc/go-ui/ui/uiobjs.go:1265 +0xac
github.com/visualfc/go-ui/ui.Main(0x400d12, 0x100000001, 0xc, 0x0)
/home/kornel/dokumenty/programowanie/golang/test1/src/github.com/visualfc/go-ui/ui/ui.go:17 +0x35
main.main()
/home/kornel/dokumenty/programowanie/golang/test1/src/github.com/visualfc/go-ui/examples/minimal.go:17 +0xc4

goroutine 2 [syscall]:
created by runtime.main
/usr/lib/go/src/pkg/runtime/proc.c:221

The problem occurs on Gentoo on amd64,
$ qmake -v
QMake version 2.01a
Using Qt version 4.8.2 in /usr/lib64/qt4
$ go version
go version go1.0.3