message: Fix crashes when $HOME is not set
  In case HOME environment variable hasn't been set, getenv returns
  NULL, which leads to a crash.
diff: @@ -301,7 +301,8 @@ string LayerRegistrationPath(LayerPath path)
  if(xdg && FileIO::exists(xdg))
  return string(xdg) + "/vulkan/implicit_layer.d/renderdoc_capture.json";
  - return string(getenv("HOME")) +
  + const char *home_path = getenv("HOME");
  + return string(home_path != NULL ? home_path : "") +
  "/.local/share/vulkan/implicit_layer.d/renderdoc_capture.json";
  }
  default: break;
  @@ -330,7 +331,10 @@ bool VulkanReplay::CheckVulkanLayer(VulkanLayerFlags &flags, std::vector<std::st
  {
  // see if the user has suppressed all this checking as a "I know what I'm doing" measure
  - if(FileExists(string(getenv("HOME")) + "/.renderdoc/ignore_vulkan_layer_issues"))
  + const char *home_path = getenv("HOME");
  + if(home_path == NULL)
  + home_path = "";
  + if(FileExists(string(home_path) + "/.renderdoc/ignore_vulkan_layer_issues"))
  {
  flags = VulkanLayerFlags::ThisInstallRegistered;
  return false;
  