[clang-tools-extra] [clang-doc][fix] crashes when generating HTML without `--repository` (PR #131698)

[Paul Kirth via cfe-commits]

ilovepi wrote:

> @ilovepi I see you opened a PR to solve the same issue [here](https://github.com/llvm/llvm-project/pull/131939). Wouldn't be better if I continue working on it with your suggestions? 😅

I'm fine either way, but I wanted some kind of testing so I could verify the fix.


https://github.com/llvm/llvm-project/pull/131698