chore(tests): renovate tests

Author: singerla

__tests__/modify-chart-scatter.test.ts

@@ -49,5 +49,5 @@ test('create presentation, add and modify a scatter chart.', async () => {
     })
     .write(`modify-chart-scatter.test.pptx`)
 
-  expect(result.charts).toBe(2);
+  expect(result.charts).toBe(4);
 });

src/helper/xml-elements.ts

@@ -91,7 +91,9 @@ export default class XmlElements {
     dPt.appendChild(this.spPr());
 
     const nextSibling = this.element.getElementsByTagName('c:cat')[0];
-    nextSibling.parentNode.insertBefore(dPt, nextSibling)
+    if(nextSibling) {
+      nextSibling.parentNode.insertBefore(dPt, nextSibling)
+    }
 
     return this;
   }