bug报错

```
[MCP-Server-Chart] 2026-07-02T09:45:29.878Z ℹ️ calling tool generate_area_chart {
data: [
{ time: '2024', value: 51 },
{ time: '2025', value: 74 },
{ time: '2026', value: 107 },
{ time: '2027', value: 155 },
{ time: '2028', value: 225 },
{ time: '2029', value: 326 },
{ time: '2030', value: 471 }
],
stack: false,
style: null,
theme: 'default',
width: 800,
height: 450,
title: '全球AI智能体市场规模增长趋势（单位：亿美元）',
axisXTitle: '年份',
axisYTitle: '市场规模（亿美元）'
}
[MCP-Server-Chart] 2026-07-02T09:45:29.878Z ℹ️ Calling tool: generate_area_chart
[MCP-Server-Chart] 2026-07-02T09:45:30.255Z ❌ Failed to generate chart: Cannot read properties of null (reading 'texture')
evalmachine.:10
const _texture = texture || style.texture || "default";
^

TypeError: Cannot read properties of null (reading 'texture')
at evalmachine.:10:35
at Script.runInContext (node:vm:149:12)
at Script.runInNewContext (node:vm:154:17)
at execute (/var/task/code/ApiControlleroneclipPost.ts:13:66)
at executor (/var/task/code/ApiControlleroneclipPost.ts:13:66)
at (/var/task/code/ApiControlleroneclipPost.ts:13:66)
at new Promise ()
at getSandboxSSRBuffer (/var/task/code/ApiControlleroneclipPost.ts:13:66)
at ScreenShotService.oneclip (/var/task/code/ApiControlleroneclipPost.ts:13:66)
at process.processTicksAndRejections (node:internal/process/task_queues:95:5).
2026-07-02 17:45:30 - workflow.workflow_agent - ERROR - MCP error -32603: Failed to generate chart: Cannot read properties of null (reading 'texture')
evalmachine.:10
const _texture = texture || style.texture || "default";
^

TypeError: Cannot read properties of null (reading 'texture')
at evalmachine.:10:35
at Script.runInContext (node:vm:149:12)
at Script.runInNewContext (node:vm:154:17)
at execute (/var/task/code/ApiControlleroneclipPost.ts:13:66)
at executor (/var/task/code/ApiControlleroneclipPost.ts:13:66)
at (/var/task/code/ApiControlleroneclipPost.ts:13:66)
at new Promise ()
at getSandboxSSRBuffer (/var/task/code/ApiControlleroneclipPost.ts:13:66)
at ScreenShotService.oneclip (/var/task/code/ApiControlleroneclipPost.ts:13:66)
at process.processTicksAndRejections (node:internal/process/task_queues:95:5)

```

Start at the generate_area_chart tool and trace how its null style value reaches the rendering path shown in ApiControlleroneclipPost.ts. Reproduce the request from the issue, then verify that the same chart generates successfully when style is null and no texture-related exception is raised.

Written by the indexing model from the issue text.