OBJ DecodeReader crashing without valid mtl

[CannibalVox]

In #29, support was added for obj files with no valid material file- a plain gray material is loaded instead. In #101, a panic was discovered when no valid material file was available, and that was fixed. There is now a new panic:

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x18 pc=0x7ff737213039]

goroutine 1 [running, locked to thread]:
bufio.(*Reader).fill(0xc000387ab0)
        C:/Program Files/Go/src/bufio/bufio.go:101 +0xd9
bufio.(*Reader).ReadSlice(0xc000387ab0, 0x0)
        C:/Program Files/Go/src/bufio/bufio.go:360 +0x2f
bufio.(*Reader).collectFragments(0x7ff7371fbe8e, 0x0)
        C:/Program Files/Go/src/bufio/bufio.go:435 +0x74
bufio.(*Reader).ReadString(0x0, 0x2a)
        C:/Program Files/Go/src/bufio/bufio.go:483 +0x2b
github.com/g3n/engine/loader/obj.(*Decoder).parse(0xc0001860c0, {0x0, 0x0}, 0xc000387c48)
        C:/msys64/mingw64/pkg/mod/github.com/g3n/engine@v0.2.0/loader/obj/obj.go:407 +0x1be
github.com/g3n/engine/loader/obj.DecodeReader({0x20a37fa8a20, 0xc00009a0f0}, {0x0, 0x0})
        C:/msys64/mingw64/pkg/mod/github.com/g3n/engine@v0.2.0/loader/obj/obj.go:156 +0x2ad
main.(*HelloTriangleApplication).loadModel(0xc00018a000)
        C:/Users/Stephen/projects/VKng/examples/vulkan_tutorial/27_model_loading/main.go:1399 +0x6e
main.(*HelloTriangleApplication).initVulkan(0xc00018a000)
        C:/Users/Stephen/projects/VKng/examples/vulkan_tutorial/27_model_loading/main.go:271 +0x1c5
main.(*HelloTriangleApplication).Run(0xc00018a000)
        C:/Users/Stephen/projects/VKng/examples/vulkan_tutorial/27_model_loading/main.go:162 +0x53
main.main()
        C:/Users/Stephen/projects/VKng/examples/vulkan_tutorial/27_model_loading/main.go:2021 +0x2a
exit status 2

This is running in go 1.17- it's possible a change was made in a recent go version that causes buffer reading to panic with a nil reader where it didn't previously.

[danaugrs]

Hi Stephen!
I tested loading an obj file without a material file and it seemed to use the default material as expected, no panic.
(master branch, Go1.17.1)
Can you send me the offending obj file?

[CannibalVox]

The obj file and also the code I used to repro. The obj file needs to be in the mesh folder for the example.

https://gist.github.com/CannibalVox/f59a6fc6c5a7af6cfa41fd0bbf6d9e82

[danaugrs]

Fixed by 549ee35. Thanks!