turnip,lvp: Crash in ycbcr lowering in GFXBench Aztec Ruins Vulkan tests

E.g. for Turnip + VN the crash looks like:

Crash reason:  SIGSEGV /0x00000000
Crash address: 0x18
Process uptime: not available

Thread 0 (crashed)
 0  libvulkan_freedreno.so!tu_shader_create [tu_shader.c : 477 + 0x0]
     r0 = 0x00000004    r1 = 0x00000000    r2 = 0x00000005    r3 = 0xe9b09160
     r4 = 0x00000001    r5 = 0xe9d89548    r6 = 0x00000000    r7 = 0x0000000b
     r8 = 0xe9b0832c    r9 = 0xe9f11c18   r10 = 0x00000000   r12 = 0x00000001
     fp = 0xec8fe84c    sp = 0xec8fe7b0    lr = 0x00000002    pc = 0xed5e8926
    Found by: given as instruction pointer in context
 1  libvulkan_freedreno.so!tu_CreateGraphicsPipelines [tu_pipeline.c : 2429 + 0x9]
     r4 = 0x00000000    r5 = 0x00000003    r6 = 0x00000004    r7 = 0xe9e16988
     r8 = 0x00000000    r9 = 0x00000000   r10 = 0xec8feabc    fp = 0xeabacb18
     sp = 0xec8fea40    pc = 0xed5e222f
    Found by: call frame info
 2  libvirglrenderer.so.1!vkr_dispatch_vkCreateGraphicsPipelines [vkr_pipeline_gen.h : 278 + 0xb]
     r4 = 0x00000000    r5 = 0x00000000    r6 = 0xeabb35f8    r7 = 0x00000000
     r8 = 0x00000000    r9 = 0xec8fec80   r10 = 0x04c28f20    fp = 0xebf04700
     sp = 0xec8fec30    pc = 0xedbbeebd
    Found by: call frame info
 3  libvirglrenderer.so.1!vn_dispatch_vkCreateGraphicsPipelines [vn_protocol_renderer_pipeline.h : 1488 + 0x5]
     r4 = 0xb4000078    r5 = 0x00000000    r6 = 0xec8fec80    r7 = 0x690441d0
     r8 = 0xedc9d2d8    r9 = 0x00000000   r10 = 0x04c28ff8    fp = 0x00000000
     sp = 0xec8fec80    pc = 0xedb946f7
    Found by: call frame info
 4  libvirglrenderer.so.1!vkr_context_submit_cmd [vn_protocol_renderer_dispatches.h : 451 + 0x5]
     r4 = 0x00000041    r5 = 0x00000000    r6 = 0x04c28ff8    r7 = 0x00000000
     r8 = 0x04c28f60    r9 = 0xedc25288   r10 = 0x04c28fb8    fp = 0xedc10f08
     sp = 0xec8fece0    pc = 0xedb88b53
    Found by: call frame info
 5  libvirglrenderer.so.1!vkr_ring_thread [vkr_ring.c : 325 + 0x1]
     r4 = 0x04c29598    r5 = 0x000012cc    r6 = 0x00000000    r7 = 0x04c2d758
     r8 = 0x04c29604    r9 = 0x000012cc   r10 = 0x0000ae0c    fp = 0x04c29580
     sp = 0xec8fed08    pc = 0xedbc19b1
    Found by: call frame info
 6  libpthread.so.0 + 0x53ad
     r4 = 0x00000000    r5 = 0xec8ff5f8    r6 = 0xffea48f6    r7 = 0xec8fed70
     r8 = 0xec8ff3e0    r9 = 0xedc95010   r10 = 0x00000000    fp = 0xec8feea0
     sp = 0xec8fed70    pc = 0xedac03af
    Found by: call frame info

static void
lower_tex_ycbcr(const struct tu_pipeline_layout *layout,
                nir_builder *builder,
                nir_tex_instr *tex)
{
   int deref_src_idx = nir_tex_instr_src_index(tex, nir_tex_src_texture_deref);
   assert(deref_src_idx >= 0);
   nir_deref_instr *deref = nir_src_as_deref(tex->src[deref_src_idx].src);

   nir_variable *var = nir_deref_instr_get_variable(deref);
   const struct tu_descriptor_set_layout *set_layout =
      layout->set[var->data.descriptor_set].layout;   <============= CRASH IS HERE
   const struct tu_descriptor_set_binding_layout *binding =
      &set_layout->binding[var->data.binding];
   const struct tu_sampler_ycbcr_conversion *ycbcr_samplers =
      tu_immutable_ycbcr_samplers(set_layout, binding);

   if (!ycbcr_samplers)
      return;