Avoids sanitizer errors like:
```
../src/intel/vulkan/anv_pipeline_cache.c:409:4: runtime error: null pointer passed as argument 1, which is declared to never be null
../src/intel/vulkan/anv_descriptor_set.c:696:4: runtime error: null pointer passed as argument 1, which is declared to never be null
../src/intel/vulkan/anv_descriptor_set.c:2709:10: runtime error: null pointer passed as argument 1, which is declared to never be null
../src/intel/vulkan/anv_descriptor_set.c:2709:10: runtime error: null pointer passed as argument 2, which is declared to never be null
```
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32098>
Matt Turner
b6d11ba5b4