Fix repeated empty workspaces after changing the grid size.

There are specific scenarios when you can force an extra empty
workspace after changing the grid, fortunately there is a
function that removes empty workspaces.

Fix:229349287
Test: Add a widget in a new empty workspace page, change the
grid then remove the widget in the new grid size then return
to the previous grid and it shouldn't have an empty workspace.

Change-Id: I7b73ae2ca058bc84b3b361930e3dc856c045281b