Fix unwrap ICE from struct field ident in AST pretty

[chenyukang]

Fixes #140333

[rustbot]

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[rustbot]

This PR changes a file inside tests/crashes. If a crash was fixed, please move into the corresponding ui subdir and add 'Fixes #' to the PR description to autoclose the issue upon merge.

[compiler-errors]

Sorry for the delay on the review. I don't believe this is the right fix. Namely, I think the root cause is a bit involved -- see #142393.

[chenyukang]

Sorry for the delay on the review. I don't believe this is the right fix. Namely, I think the root cause is a bit involved -- see #142393.

I have read your code, it is more complicated than I thought, thank you. I'm closing this PR now.