Crash when using Glad on Vulkan with NSight
When using glad for Vulkan with NSight enabled, there's a crash when calling gladLoaderLoadVulkan.

Callstack:
- glad_vk_has_extension(const char *) Line 12549 
- glad_vk_find_extensions_vulkan(VkPhysicalDevice_T * physical_device) Line 12566
- gladLoadVulkanUserPtr(VkPhysicalDevice_T * physical_device, void()(void *, const char *) load, void * userptr) Line 12873
- gladLoaderLoadVulkan(VkInstance_T *) Line 13518

`static int glad_vk_has_extension(const char *name, uint32_t extension_count, char **extensions) {
    uint32_t i;

    for (i = 0; i < extension_count; ++i) {
        if(strcmp(name, extensions[i]) == 0) {  ----------> Crash here accessing an invalid index
            return 1;
        }
    }

    return 0;
}`

The problem is in the "glad_vk_get_extensions function". For some weird reason, the first time calling glad_vkEnumerateDeviceExtensionProperties(physical_device, NULL, &device_extension_count, NULL); it returns device_extension_count = 116.

But the second is called (a couple of lines later) glad_vkEnumerateDeviceExtensionProperties(physical_device, NULL, &device_extension_count, ext_properties); it returns device_extension_count = 115.

This makes the variable "total_extension_count" have the wrong value. Causing a crash later when accessing index 115 in the extension arrays.

Apparently this is due to a bug in the loader: https://github.com/KhronosGroup/Vulkan-Loader/issues/348
