Remove debug-only assertion from vulkan::api::Command::Command as the buffer can legitimately be null. (#51160)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/51160
Test Plan: Imported from OSS
Reviewed By: IvanKobzarev
Differential Revision: D26131252
Pulled By: AshkanAliabadi
fbshipit-source-id: 69f324ceed711753d77ab7c6b6a20a29cdbdf5f9
