chore: :arrow_up: Update ggml-org/llama.cpp to `d6588daa800058dfa54f1d7ea695b1a810c8ae18` (#10093)

* :arrow_up: Update ggml-org/llama.cpp

Signed-off-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* fix(llama-cpp): skip begin-of-stream null partial in PredictStream

Upstream llama.cpp (ggml-org/llama.cpp#23884), pulled in by this bump,
now emits an initial "begin" partial whose to_json() returns null. It
exists only to signal the HTTP layer to flush 200 status headers before
any token is produced.

gRPC has no such concept, and PredictStream had no guard: the null result
was fed straight into build_reply_from_json, which threw an uncaught
exception. That surfaced as a generic "Unexpected error in RPC handling"
and the task was cancelled the instant it launched, breaking the
PredictStream e2e spec.

Skip null results in both the first-result handling and the streaming
loop, mirroring upstream's own `if (first_result_json == nullptr)` guard.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Assisted-by: Claude:claude-opus-4-8 [Claude Code]

---------

Signed-off-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: mudler <2420543+mudler@users.noreply.github.com>
Co-authored-by: Ettore Di Giacinto <mudler@localai.io>