Panic if ignore path or file does not exist

[nuke-web3]

Describe the bug

mlc 1.71 panics for ignore-path = [""] or in any case a file does not exist like ignore-path = ["node_modules", "html-slides", "html-book"] (for me these are build artifacts, should be .gitignore respected?)

To Reproduce
Steps to reproduce the behavior:

1. https://github.com/nuke-web3/book/actions/runs/9467833203/job/26082787141 see the log and workflow file used plus this config

Expected behavior
If a file or path does not exist, it is simply skipped.

Ideally this would use a glob match, but that can be a separate feat req 😀 .