panvk: Add check for null fence

Signed-off-by: Manas Chaudhary <manas.chaudhary@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14108>

src/panfrost/vulkan/panvk_sync.c

@@ -238,6 +238,9 @@ panvk_DestroyFence(VkDevice _device, VkFence _fence,
    VK_FROM_HANDLE(panvk_device, device, _device);
    VK_FROM_HANDLE(panvk_fence, fence, _fence);
 
+   if (!fence)
+      return;
+
    sync_destroy(device, &fence->syncobj);
    vk_object_free(&device->vk, pAllocator, fence);
 }