[vulkan] Fix bug in empty root buffer (#2807)
[vulkan] Fix bug in empty root buffer (#2807)

* [vulkan] Fix bug in empty root buffer

* Auto Format

* typo

Co-authored-by: Taichi Gardener <52844ac7498fba84f633481a7c3ae54491811c81@gmail.com>
yuanming-hu/taichi,yuanming-hu/taichi,yuanming-hu/taichi,yuanming-hu/taichi