fix(charts): prevent TypeError crash when streaming nullish data

[serhiizghama]

Problem

Closes #355.

Every public chart component (BarChart, BarChartCondensed, LineChart, AreaChart, PieChart, RadarChart, ScatterChart, …) reads its data prop directly — getDataKeys(data, …), data.length, [...data].sort() — assuming data is always an array.

While generative UI is streaming, data can momentarily be null/undefined before the full payload has been parsed. Passing that into the chart internals throws:

TypeError: Cannot read properties of null (reading '0')   // getDataKeys
TypeError: Cannot read properties of null (reading 'length')
TypeError: data is not iterable                            // [...data]

This crashes the whole render mid-stream.

Solution

Add a small shared helper normalizeChartData() in Charts/utils/dataUtils.ts that coerces data to an array, and call it once at the top of each chart component so the rest of the component always works with a real array (an empty chart instead of a crash).

Two details that make it safe:

• Stable empty reference — when data is nullish it falls back to a single shared EMPTY_CHART_DATA constant, so normalization never creates a new [] on every render (which would change identity and defeat the existing useMemo/React.memo optimizations). When data is a valid array it is returned by reference, unchanged.
• getDataKeys() is also made null-safe (data?.[0]) as defense-in-depth, since it is the shared first access point.

The genui-lib schema layer already guards its own path via hasAllProps/buildChartData; this PR hardens the public exported chart components themselves, which are part of the package surface and can be rendered directly by consumers (and during streaming).

This matches the approach agreed on in the issue thread (Array.isArray(data) ? data : [], applied consistently across all chart types).

Testing

• pnpm --filter @openuidev/react-ui typecheck — passes
• pnpm --filter @openuidev/react-ui ci (lint:check + format:check) — passes
• Verified normalizeChartData(null)/(undefined) return the same stable empty array, valid arrays pass through by reference, and getDataKeys(null) returns [] instead of throwing.

[vishxrad]

Thanks for the PR. We’re going to address this at the genui-lib streaming/parser layer rather than in each chart component. Please keep this PR open for now while we implement and verify that approach. Once the replacement is confirmed, we’ll close this PR as superseded. We’ll track the work in #355.