configure_graphics: Fix handling of broken Vulkan

The VSync combobox wouldn't populate if there was no Vulkan device,
which caused issues with trying to set VSync on other backends.

This also adds another layer to GetCurrentGraphicsBackend to check for
broken Vulkan and return OpenGL instead of Vulkan.

src/yuzu/configuration/configure_graphics.cpp

@@ -193,13 +193,9 @@ void ConfigureGraphics::PopulateVSyncModeSelection() {
                             : vsync_mode_combobox_enum_map[current_index];
     int index{};
     const int device{vulkan_device_combobox->currentIndex()}; //< current selected Vulkan device
-    if (device == -1) {
-        // Invalid device
-        return;
-    }
 
     const auto& present_modes = //< relevant vector of present modes for the selected device or API
-        backend == Settings::RendererBackend::Vulkan ? device_present_modes[device]
+        backend == Settings::RendererBackend::Vulkan && device > -1 ? device_present_modes[device]
                                                                     : default_present_modes;
 
     vsync_mode_combobox->clear();
@@ -497,6 +493,7 @@ void ConfigureGraphics::RetrieveVulkanDevices() {
 }
 
 Settings::RendererBackend ConfigureGraphics::GetCurrentGraphicsBackend() const {
+    const auto selected_backend = [=]() {
         if (!Settings::IsConfiguringGlobal() && !api_restore_global_button->isEnabled()) {
             return Settings::values.renderer_backend.GetValue(true);
         }
@@ -504,4 +501,11 @@ Settings::RendererBackend ConfigureGraphics::GetCurrentGraphicsBackend() const {
             combobox_translations.at(Settings::EnumMetadata<Settings::RendererBackend>::Index())
                 .at(api_combobox->currentIndex())
                 .first);
+    }();
+
+    if (selected_backend == Settings::RendererBackend::Vulkan &&
+        UISettings::values.has_broken_vulkan) {
+        return Settings::RendererBackend::OpenGL;
+    }
+    return selected_backend;
 }