llvmpipe: Handle NULL views in llvmpipe_cleanup_stage_sampling

This is the only barrier to lavapipe fully working in RenderDoc.

Fixes: 21864bdaae ("llvmpipe: unmap display target of shader image/sampler")

Signed-off-by: Joshua Ashton <joshua@froggi.es>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11856>

src/gallium/drivers/llvmpipe/lp_state_sampler.c

@@ -422,10 +422,11 @@ llvmpipe_cleanup_stage_sampling(struct llvmpipe_context *ctx,
 
    for (i = 0; i < num; i++) {
       struct pipe_sampler_view *view = views[i];
-      assert(view);
-      struct pipe_resource *tex = view->texture;
-      if (tex)
-         llvmpipe_resource_unmap(tex, 0, 0);
+      if (view) {
+         struct pipe_resource *tex = view->texture;
+         if (tex)
+            llvmpipe_resource_unmap(tex, 0, 0);
+      }
    }
 }