Column unselecting/resizing doesn't work when TableView has one column

[svgol]

Steps to reproduce:

1. Create a TableView with one column (by default Gorm creates one with 2 columns).
2. Select the column to highlight it.
3. Try to unselect. It doesn't work, neither clicking on it nor on empty space around.
   Resizing is unavailable too. The corresponding cursor doesn' t appear over the column title border.
4. The only solution is to select the TableView and change its layout to 2 columns temporarily.

[svgol]

Ubuntu 20.04
all GNUstep libs and Gorm from the branches 'master'

[gcasa]

This can be worked around in the inspector, but I have confirmed it.