SWT GridLayouts require every cell to have content. If you want an empty cell, add a blank label. If you try to add a blank composite, the cell will likely be larger than what you want since composites seem to have a somewhat large minimum size (at least in a grid layout).
... until the collector arrives ...
This "blog" is really just a scratchpad of mine. There is not much of general interest here. Most of the content is scribbled down "live" as I discover things I want to remember. I rarely go back to correct mistakes in older entries. You have been warned :)