Depth stencil state is not present when fragment stage is writing to frag_depth

Questions
1

Hello, guys. Does anyone know why this error occur? It confused me a lot.
Sometimes, it happend when the depth buffer of a rendertarget is disabled.

Depth stencil state is not present when fragment stage ([ShaderModule "fragment"], [EntryPoint "main"]) is writing to frag_depth.
 - While validating fragment state.
 - While calling [Device].CreateRenderPipeline([RenderPipelineDescriptor "renderPipeline_GTAO_38"]).