Bad behaviour of Supr button when altering the length of a column with the Alter Table wizard (4334608)

When pressing supr button  to remove the lenght to the column to enter a new one, the complete column table is deleted.
This should not happen as the focus is not in the column.

Steps to reproduce the problem:

1. Go to Object Explorer
2. Select a table
3. R-click and select Alter table
4. Go to Columns and select a varchar column
5. Go to Lenght property and select the value with double click.
6. Now press the supr button.

The whole column is removed.
In version 5.5 just the lenght of the column is deleted and you can enter a new one.