log output of attempting to take a screen capture of the currently focused window with gorobot

stdout

version  v0.90.0.896, Sierra Nevada!
{CgID:10453 AxID:73413584}
369
error  <nil>
iTerm2
811008, 512, 48, 124
Assertion failed: (bitmap != NULL), function createPNGWriteInfo, file /Users/alex/go/src/github.com/go-vgo/robotgo/screen/../base/png_io_c.h, line 187.
SIGABRT: abort
PC=0x7fff68bc62c6 m=0 sigcode=0

goroutine 0 [idle]:
runtime: unknown pc 0x7fff68bc62c6
stack: frame={sp:0x7ffeefbff1f8, fp:0x0} stack=[0x7ffeefb80350,0x7ffeefbff3c0)
00007ffeefbff0f8:  0000000000000000  00000000043fe000
00007ffeefbff108:  00007fff68b59f45  00007ffeefbff180
00007ffeefbff118:  00007fff68c76bcb  0000000000000000
00007ffeefbff128:  00007ffeefbff150  00007ffeefbff190
00007ffeefbff138:  0000000000000000  00007fff68b59f46
00007ffeefbff148:  00007ffeefbff198  6f695f676e702f65
00007ffeefbff158:  000000000428849a  0000000004287539
00007ffeefbff168:  00000000043fe000  00000000000000bb
00007ffeefbff178:  0000000004287c1e  00007ffeefbff260
00007ffeefbff188:  00007fff68c75084  0000003000000030
00007ffeefbff198:  00007ffeefbff270  00007ffeefbff1b0
00007ffeefbff1a8:  0000000000000000  0000000000000003
00007ffeefbff1b8:  7fffffffffffffff  0000000004287539
00007ffeefbff1c8:  000000000428849a  00007fff9f3f4030
00007ffeefbff1d8:  00007fff9f3f09a8  00007fff68b0fbb8
00007ffeefbff1e8:  0000000000000000  00007ffeefbff230
00007ffeefbff1f8: <00007fff68c81bf1  00000000125f45c0
00007ffeefbff208:  00007ffeefbff248  00000000043fe028
00007ffeefbff218:  00000000043fe000  00000000000000bb
00007ffeefbff228:  0000000004287c1e  00007ffeefbff260
00007ffeefbff238:  00007fff68b306a6  00007ffeefbff260
00007ffeefbff248:  00007fffffffffdf  ffffffffffe7ffff
00007ffeefbff258:  000000000428849a  00007ffeefbff2a0
00007ffeefbff268:  00007fff68af920d  000000000450fd20
00007ffeefbff278:  0000000000000000  0000000000000000
00007ffeefbff288:  00000000041944cd  000000000450fd20
00007ffeefbff298:  000000c0000c5d88  00007ffeefbff2e0
00007ffeefbff2a8:  000000000411a864  00007fff9f3f4030
00007ffeefbff2b8:  0000000000000000  00007fff9f3f4030
00007ffeefbff2c8:  00000000041944cd  00000000ffffffff
00007ffeefbff2d8:  000000c0000c5d88  00007ffeefbff320
00007ffeefbff2e8:  000000000411a52d  0000000000000001
runtime: unknown pc 0x7fff68bc62c6
stack: frame={sp:0x7ffeefbff1f8, fp:0x0} stack=[0x7ffeefb80350,0x7ffeefbff3c0)
00007ffeefbff0f8:  0000000000000000  00000000043fe000
00007ffeefbff108:  00007fff68b59f45  00007ffeefbff180
00007ffeefbff118:  00007fff68c76bcb  0000000000000000
00007ffeefbff128:  00007ffeefbff150  00007ffeefbff190
00007ffeefbff138:  0000000000000000  00007fff68b59f46
00007ffeefbff148:  00007ffeefbff198  6f695f676e702f65
00007ffeefbff158:  000000000428849a  0000000004287539
00007ffeefbff168:  00000000043fe000  00000000000000bb
00007ffeefbff178:  0000000004287c1e  00007ffeefbff260
00007ffeefbff188:  00007fff68c75084  0000003000000030
00007ffeefbff198:  00007ffeefbff270  00007ffeefbff1b0
00007ffeefbff1a8:  0000000000000000  0000000000000003
00007ffeefbff1b8:  7fffffffffffffff  0000000004287539
00007ffeefbff1c8:  000000000428849a  00007fff9f3f4030
00007ffeefbff1d8:  00007fff9f3f09a8  00007fff68b0fbb8
00007ffeefbff1e8:  0000000000000000  00007ffeefbff230
00007ffeefbff1f8: <00007fff68c81bf1  00000000125f45c0
00007ffeefbff208:  00007ffeefbff248  00000000043fe028
00007ffeefbff218:  00000000043fe000  00000000000000bb
00007ffeefbff228:  0000000004287c1e  00007ffeefbff260
00007ffeefbff238:  00007fff68b306a6  00007ffeefbff260
00007ffeefbff248:  00007fffffffffdf  ffffffffffe7ffff
00007ffeefbff258:  000000000428849a  00007ffeefbff2a0
00007ffeefbff268:  00007fff68af920d  000000000450fd20
00007ffeefbff278:  0000000000000000  0000000000000000
00007ffeefbff288:  00000000041944cd  000000000450fd20
00007ffeefbff298:  000000c0000c5d88  00007ffeefbff2e0
00007ffeefbff2a8:  000000000411a864  00007fff9f3f4030
00007ffeefbff2b8:  0000000000000000  00007fff9f3f4030
00007ffeefbff2c8:  00000000041944cd  00000000ffffffff
00007ffeefbff2d8:  000000c0000c5d88  00007ffeefbff320
00007ffeefbff2e8:  000000000411a52d  0000000000000001

goroutine 1 [syscall]:
runtime.cgocall(0x411d3d0, 0xc0000c5d88, 0x29)
	/usr/local/go/src/runtime/cgocall.go:128 +0x5e fp=0xc0000c5d50 sp=0xc0000c5d18 pc=0x40053fe
github.com/go-vgo/robotgo._Cfunc_bitmap_save(0x0, 0x4510720, 0x1, 0x0)
	_cgo_gotypes.go:350 +0x4e fp=0xc0000c5d88 sp=0xc0000c5d50 pc=0x41125ce
github.com/go-vgo/robotgo.SaveBitmap.func1(0x0, 0x4510720, 0x4510001, 0x8)
	/Users/alex/go/src/github.com/go-vgo/robotgo/robotgo.go:1079 +0x6a fp=0xc0000c5dc0 sp=0xc0000c5d88 pc=0x4112e3a
github.com/go-vgo/robotgo.SaveBitmap(0x0, 0x4192de5, 0x8, 0x0, 0x0, 0x0, 0x0, 0x0)
	/Users/alex/go/src/github.com/go-vgo/robotgo/robotgo.go:1079 +0x7b fp=0xc0000c5e08 sp=0xc0000c5dc0 pc=0x4112bbb
main.main()
	/Users/alex/go/src/github.com/amlwwalker/experiments/robotgo/main.go:22 +0x546 fp=0xc0000c5f98 sp=0xc0000c5e08 pc=0x4115a16
runtime.main()
	/usr/local/go/src/runtime/proc.go:201 +0x207 fp=0xc0000c5fe0 sp=0xc0000c5f98 pc=0x402d197
runtime.goexit()
	/usr/local/go/src/runtime/asm_amd64.s:1333 +0x1 fp=0xc0000c5fe8 sp=0xc0000c5fe0 pc=0x40556e1

rax    0x0
rbx    0x125f45c0
rcx    0x7ffeefbff1f8
rdx    0x0
rdi    0x307
rsi    0x6
rbp    0x7ffeefbff230
rsp    0x7ffeefbff1f8
r8     0xbb
r9     0xcccccccccccccccd
r10    0x0
r11    0x206
r12    0x307
r13    0x43fe000
r14    0x6
r15    0x2d
rip    0x7fff68bc62c6
rflags 0x206
cs     0x7
fs     0x0
gs     0x0
exit status 2