[vk, renderdoc] (VUID-02997) avoid vk_image_view as VK_NULL_HANDLE when feature nullDescriptor is unavailable (#4056)

This minor change in src\video_core\renderer_vulkan\pipeline_helper.h allows renderdoc capture on mhr sunbreak.
Maybe it sanitizes some crashes on old vulkan GPUs.

Device log (nvidia kepler gpu vulkan 1.1.117):
[  17.605262] Render.Vulkan <Info> video_core\vulkan_common\vulkan_device.cpp:1041:GetSuitability: Device doesn't support feature nullDescriptor

VUID-VkWriteDescriptorSet-descriptorType-02997
For sampled/combined/storage image descriptors, Khronos says imageView must be valid or VK_NULL_HANDLE
(https://docs.vulkan.org/refpages/latest/refpages/source/VkPhysicalDeviceRobustness2FeaturesKHR.html)

but then it says: if nullDescriptor is not enabled, imageView must not be VK_NULL_HANDLE.
(https://docs.vulkan.org/spec/latest/chapters/descriptorsets.html)
nullDescriptor is exactly the feature that allows descriptors to be written with null handles.

The fix relies on conditionally replacing the null sampled view with Eden’s dummy null-image-view object (ImageView constructor checks HasNullDescriptor which checks features.robustness2.nullDescriptor. cheap checks, and only for null handles, so no notable cost).

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4056
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>

src/video_core/renderer_vulkan/pipeline_helper.h

@@ -203,7 +203,11 @@ inline void PushImageDescriptors(TextureCache& texture_cache,
             const VideoCommon::ImageViewId image_view_id{(views++)->id};
             const VideoCommon::SamplerId sampler_id{*(samplers++)};
             ImageView& image_view{texture_cache.GetImageView(image_view_id)};
-            const VkImageView vk_image_view{image_view.Handle(desc.type)};
+            VkImageView vk_image_view{image_view.Handle(desc.type)};
+            if (vk_image_view == VK_NULL_HANDLE) {
+                const VkImageView null_image_view{texture_cache.GetImageView(VideoCommon::NULL_IMAGE_VIEW_ID).Handle(desc.type)};
+                if (null_image_view != VK_NULL_HANDLE) vk_image_view = null_image_view;
+            }
             const Sampler& sampler{texture_cache.GetSampler(sampler_id)};
             const bool use_fallback_sampler{sampler.HasAddedAnisotropy() &&
                                             !image_view.SupportsAnisotropy()};