language server provides no reply if `LookupFile` fails

[zygoloid]

Description of the bug:

handle_document_symbol.cpp and handle_formatting.cpp return; without calling on_done when LookupFile fails. Instead of returning an error they emit a diagnostic and leave the LSP client waiting forever for a reply.

What did you do, or what's a simple way to reproduce the bug?

No response

What did you expect to happen?

No response

What actually happened?

No response

Any other information, logs, or outputs that you want to share?

Bug was found by Claude in passing when working on a separate LSP feature.

[abhinav-phi]

hmm i see the issue.. on LookupFile fail both handlers just return without calling on_done so client keeps waiting forever

my plan is.. call on_done with error reply instead of bare return same like nearby handlers do.. maybe this fix it and i guess this is optimal too

opening the PR for this very soon..