Error is thrown when delete lats child column from a column group

[nrobakova]

Description

Error is thrown when delete lats child column from a column group

• igniteui-angular version: 8.2
• browser: n/a

Steps to reproduce

1. Open sample
2. Click delete button twice

Result

An error is returned when delete the last column

Expected result

There should be no errors and the column should be removed

Attachments

Attach a sample if available, and screenshots, if applicable.