fix(bolt-sidecar): return error when no bids

[estensen]

Fixes #515

Before it tried to get an error from 204, which didn't exist.

{"duration":"0.119152","level":"info","method":"GET","msg":"http: GET /eth/v1/builder/header_with_proofs/3203582/0x8c34059ed5607d63f7f300f16654117dfb04c5e173ef74106e782f54481430c3/0x88b876f6f2d910442b04b4ec00ffd70cc84024ed7c86ba3dcff761b2b18a230b62034ab48a08916c4118aecdbda65671 204","path":"/eth/v1/builder/header_with_proofs/3203582/0x8c34059ed5607d63f7f300f16654117dfb04c5e173ef74106e782f54481430c3/0x88b876f6f2d910442b04b4ec00ffd70cc84024ed7c86ba3dcff761b2b18a230b62034ab48a08916c4118aecdbda65671","status":204,"time":"2024-12-16T10:36:38.677Z","version":""}