[llvm] [RISCV] Fix crash when trying to remove segment (PR #146524)

[Luke Lau via llvm-commits]

https://github.com/lukel97 commented:

Thanks, can you create an MIR test in vsetvli-insert.mir that shows this?

Also would be good to clarify in the title under what exact conditions this crash happens and how this fixes it

https://github.com/llvm/llvm-project/pull/146524