[vulkan][fix] Fix unsafe direct array access (#83432)
This diff fixes an instance of unsafe array access of a sizes array.
Differential Revision: [D38710499](https://our.internmc.facebook.com/intern/diff/D38710499/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/83432
Approved by: https://github.com/kirklandsign, https://github.com/manuelcandales
