notebook: Select the Last Cell when deleting selected last cell (#13715)

* notebook: Select the Last Cell when deleting selected cell with index larger than avaialable cells

Signed-off-by: Jonah Iden <jonah.iden@typefox.io>

* better length check

Signed-off-by: Jonah Iden <jonah.iden@typefox.io>

---------

Signed-off-by: Jonah Iden <jonah.iden@typefox.io>

packages/notebook/src/browser/view-model/notebook-model.ts

@@ -314,7 +314,7 @@ export class NotebookModel implements Saveable, Disposable {
 
             // if selected cell is affected update it because it can potentially have been replaced
             if (cell === this.selectedCell) {
-                this.setSelectedCell(this.cells[cellIndex]);
+                this.setSelectedCell(this.cells[Math.min(cellIndex, this.cells.length - 1)]);
             }
         }