clCreateContext return unknown error code when create gl sharing context.

When I switch code from intel opencl sdk to the icd loader, the clCreateContext fails, but intel sdk works fine when calling clCreateContext with a GPU type device.
If I call clCreateContext without gl sharing properties, icd loader works fine.

Sample code as below:
```
cl_int err = CL_SUCCESS;
//get nvidia platform and gpu type device omitted.
cl_context_properties properties[] = {
CL_GL_CONTEXT_KHR, (cl_context_properties)wglGetCurrentContext(),
CL_WGL_HDC_KHR, (cl_context_properties)wglGetCurrentDC(),
CL_CONTEXT_PLATFORM, (cl_context_properties)targetPlatform,
0
};
cl::g_ctx = clCreateContext(properties, 1, &device, NULL, NULL, &err);//if call clCreateContext(NULL, 1, &device, NULL, NULL, &err); no error occur.
CL_CHECK(err);//this err code is -9999.
```

My Environment is: **windows 10**, **NVIDIA gtx1050ti** with driver version **R398.36 (r398_35-2) / 22.20.16.4735 (7-7-2017)**

Start with the reported clCreateContext call and its OpenGL sharing properties, then reproduce the failure on the stated Windows 10 and NVIDIA GTX 1050 Ti environment. Compare the returned -9999 error with the same call without sharing properties; done means identifying whether the ICD loader or vendor implementation is responsible and documenting a confirmed resolution.

Written by the indexing model from the issue text.