vk_pipeline_cache: Skip cache save when no pipeline cache exists

* This is the cache when loading a save state

src/video_core/renderer_vulkan/vk_pipeline_cache.cpp

@@ -148,7 +148,7 @@ void PipelineCache::LoadDiskCache() {
 }
 
 void PipelineCache::SaveDiskCache() {
-    if (!Settings::values.use_disk_shader_cache || !EnsureDirectories()) {
+    if (!Settings::values.use_disk_shader_cache || !EnsureDirectories() || !pipeline_cache) {
         return;
     }