Accept null score in hf-inference image-segmentation response

[Sanjays2402]

Closes #1430.

What

Loosens the HFInferenceImageSegmentationTask.getResponse type guard to accept score === null in addition to undefined and number.

Why

The image-segmentation output schema in packages/tasks/src/tasks/image-segmentation/inference.ts declares score as optional:

score?: number;

…but the runtime validator in packages/inference/src/providers/hf-inference.ts only accepted undefined or a number, rejecting null with:

API Implementation Error: TypeError: Invalid output: output must be of type
Array<{label:string; score:number; mask: string}>

Several HF-Inference models (e.g. jonathandinu/face-parsing, the one in the original report) return null for score on per-segment masks. That's consistent with the optional schema field, but the strict type guard treats it as a malformed response.

Diff

 (x) =>
     typeof x.label === "string" &&
     typeof x.mask === "string" &&
-    (x.score === undefined || typeof x.score === "number"),
+    (x.score === undefined || x.score === null || typeof x.score === "number"),

Out of scope

• Tightening inference.ts to make score explicitly nullable — leaving the schema as-is to avoid breaking anyone reading it.
• Other tasks: this is the only validator in hf-inference.ts whose schema declares score as optional, so the same null-acceptance change isn't symmetric across the file.

---

Note

Low Risk
Single-task response normalization in the HF-Inference provider with no auth, persistence, or API surface changes.

Overview
Fixes HF-Inference image-segmentation responses that were rejected when models return score: null (e.g. jonathandinu/face-parsing), which previously triggered a malformed-output error despite optional score in the task schema.

HFInferenceImageSegmentationTask.getResponse now accepts null in its guard and normalizes null scores to undefined so returned data matches score?: number and callers using score !== undefined behave correctly.

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