[FIX] chart: don't crash treemap without visible data

Steps to reproduce:
- in A1: "Year"
- in B1: "2025"
- create a tree map chart with Hierachy: A1 and Values: B1
- go to the design panel
- change it to "Color scale"
- hide column B

=> Crash

opw-5166581

closes #7549

Task: 5365419
Signed-off-by: Pierre Rousseau (pro) <[email protected]>

Author: LucasLefevre

src/helpers/figures/charts/runtime/chartjs_dataset.ts

@@ -692,6 +692,9 @@ function getTreeMapGroupColors(
 }
 
 function getTreeMapColorScale(tree: SunburstTreeNode[], coloringOption: TreeMapColorScaleOptions) {
+  if (tree.length === 0) {
+    return undefined;
+  }
   const treeNodesByLevel = pyramidizeTree(tree);
   const nodes = treeNodesByLevel[treeNodesByLevel.length - 1];
   const minValue = Math.min(...nodes.map((node) => node.value));

tests/figures/chart/treemap/treemap_chart_plugin.test.ts

@@ -5,6 +5,7 @@ import { TreeMapChartRuntime } from "../../../../src/types/chart/tree_map_chart"
 import {
   createSunburstChart,
   createTreeMapChart,
+  hideColumns,
   setCellContent,
   setFormat,
   updateChart,
@@ -431,6 +432,28 @@ describe("TreeMap chart", () => {
       );
     });
 
+    test("TreeMap color scale with no visible data", () => {
+      const grid = {
+        A1: "Year",
+        B1: "2025",
+      };
+      setGrid(model, grid);
+      const chartId = createTreeMapChart(model, {
+        dataSets: [{ dataRange: "A1" }],
+        labelRange: "B1",
+        dataSetsHaveTitle: false,
+        coloringOptions: {
+          type: "colorScale",
+          minColor: "#112233",
+          midColor: "#445566",
+          maxColor: "#778899",
+        },
+      });
+      expect(getTreeMapDatasetConfig(chartId).tree).toHaveLength(1);
+      hideColumns(model, ["B"]);
+      expect(getTreeMapDatasetConfig(chartId).tree).toHaveLength(0);
+    });
+
     test("TreeMap category colors with single level", () => {
       // prettier-ignore
       const grid = {