table-layout: Fix size request when there are no visible rows/cols
table-layout: Fix size request when there are no visible rows/cols

The calculation (n - 1) * spacing to compute the total spacing is
only correct for n >= 1 - if there are no visible rows/cols, the
required spacing is 0 rather than negative.

https://bugzilla.gnome.org/show_bug.cgi?id=709434

ebassi/clutter,GNOME/clutter,Distrotech/clutter,djdeath/clutter,GNOME/clutter,GNOME/clutter,jigpu/clutter,jigpu/clutter,jigpu/clutter,GNOME/clutter,djdeath/clutter,ebassi/clutter,Distrotech/clutter,Distrotech/clutter,Distrotech/clutter,jigpu/clutter,jigpu/clutter,djdeath/clutter,ebassi/clutter,djdeath/clutter,djdeath/clutter,GNOME/clutter,jigpu/clutter,djdeath/clutter,Distrotech/clutter,ebassi/clutter,ebassi/clutter,Distrotech/clutter