[llvm] [RISCV][Disassemble] Ensure the comment stream of the disassembler is set. (PR #125962)

[Craig Topper via llvm-commits]

topperc wrote:

There used to be code to handle a nullptr there, but it was removed in 1ea5ce6335c7c0e040f70de16f1080546d242b69

https://github.com/llvm/llvm-project/pull/125962