turnip: fix segmentation fault with compute pipeline

Not supported, so always set pointer to NULL

Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>

src/freedreno/vulkan/tu_pipeline.c

@@ -1924,8 +1924,8 @@ tu_CreateComputePipelines(VkDevice _device,
                                      pAllocator, &pPipelines[i]);
       if (r != VK_SUCCESS) {
          result = r;
-         pPipelines[i] = VK_NULL_HANDLE;
       }
+      pPipelines[i] = VK_NULL_HANDLE;
    }
 
    return result;