vulkan segfault with nvidia prime-run but not with intel

```sh
/usr/bin/prime-run: line 2:  7818 Segmentation fault      __NV_PRIME_RENDER_OFFLOAD=1 __VK_LAYER_NV_optimus=NVIDIA_only __GLX_VENDOR_LIBRARY_NAME=nvidia "$@
```
```sh
    GL_VENDOR:      NVIDIA Corporation
    GL_RENDERER:    NVIDIA GeForce 940M/PCIe/SSE2
    GL_VERSION:     4.6.0 NVIDIA 565.57.01
```