Describe the bug
Whenever I change 3 columns into 2 the 3rd one gets eliminated along with its content. Instead 3rd column content should shift into next row. I can get my 3rd column's content by doing undo but it is not a good approach and even I do undo Columns option sate stay on 2 and when I hit update 3rd column content get deleted.

Screenshots
Here screen record.
https://drive.google.com/file/d/1gAxuRi7FPFMKWwoDtMYlkpQxXP2F1Gjm/view?usp=sharing

To Reproduce
Steps to reproduce the behavior:

1. Go to 'edit post'
2. Add three columns and add content inside all of them.
3. Then change 3 columns to 2 columns
4. You will see 3rd columns will eliminate along with its content.

Expected behavior
Instead got eliminated 3rd column content should shift into next row.

Desktop (please complete the following information):

• OS: [Windows]
• Browser [Chrome, safari]

Additional context
Wordpress Version 4.9.8
Gutenberg Version 3.5.0