Heatmap: Fix runtime error when no data is present, add e2e test (#113242)

* Heatmap: Fix runtime error when no xAxis is present, add e2e test

* update migration test fixture

* updates from review

e2e-playwright/panels-suite/heatmap.spec.ts

@@ -0,0 +1,36 @@
+import { test, expect } from '@grafana/plugin-e2e';
+
+const DASHBOARD_UID = '5Y0jv6pVz';
+
+// test.use();
+
+test.describe('Panels test: Heatmap', { tag: ['@panels', '@heatmap'] }, () => {
+  test('renders successfully', async ({ gotoDashboardPage, selectors, page }) => {
+    const dashboardPage = await gotoDashboardPage({
+      uid: DASHBOARD_UID,
+    });
+
+    // check that gauges are rendered
+    const uplot = page.locator('.uplot');
+    await expect(uplot, 'panels are rendered').toHaveCount(2);
+
+    // check that no panel errors exist
+    const errorInfo = dashboardPage.getByGrafanaSelector(selectors.components.Panels.Panel.headerCornerInfo('error'));
+    await expect(errorInfo, 'no errors in the panels').toBeHidden();
+  });
+
+  test('"no data"', async ({ gotoDashboardPage, selectors, page }) => {
+    const dashboardPage = await gotoDashboardPage({
+      uid: DASHBOARD_UID,
+      queryParams: new URLSearchParams({ editPanel: '7' }),
+    });
+
+    const uplot = page.locator('.uplot');
+    await expect(uplot, "that uplot doesn't appear").toBeHidden();
+
+    const emptyMessage = dashboardPage.getByGrafanaSelector(selectors.components.Panels.Panel.PanelDataErrorMessage);
+    await expect(emptyMessage, 'that the empty text appears').toHaveText('No data');
+  });
+
+  // TODO tooltips, legends, and panel editing
+});