iconview: Ensure icons are at least 1x1 pixels
iconview: Ensure icons are at least 1x1 pixels

This is useful for 2 reasons:
(1) Items actually exist and are clickable
(2) Size computations don't divide by 0

I've not seen problems with this in the wild (mostly because
item-padding defaults to non-0), but noticed this while fixing other
bugs.

jadahl/gtk,Adamovskiy/gtk,jadahl/gtk,Lyude/gtk-,jigpu/gtk,Sidnioulz/SandboxGtk,jessevdk/gtk,bratsche/gtk-,grubersjoe/adwaita,ebassi/gtk,jigpu/gtk,ahodesuka/gtk,Lyude/gtk-,chergert/gtk,grubersjoe/adwaita,alexlarsson/gtk,chergert/gtk,jadahl/gtk,grubersjoe/adwaita,davidt/gtk,ahodesuka/gtk,bratsche/gtk-,davidgumberg/gtk,grubersjoe/adwaita,ebassi/gtk,ebassi/gtk,ahodesuka/gtk,davidt/gtk,chergert/gtk,msteinert/gtk,davidgumberg/gtk,alexlarsson/gtk,alexlarsson/gtk,chergert/gtk,Distrotech/gtk2,Distrotech/gtk2,Lyude/gtk-,Adamovskiy/gtk,jadahl/gtk,Sidnioulz/SandboxGtk,msteinert/gtk,alexlarsson/gtk,ahodesuka/gtk,jigpu/gtk,bratsche/gtk-,jessevdk/gtk,chergert/gtk,jigpu/gtk,chergert/gtk,jigpu/gtk,msteinert/gtk,Distrotech/gtk2,Sidnioulz/SandboxGtk,ahodesuka/gtk,grubersjoe/adwaita,davidt/gtk,Sidnioulz/SandboxGtk,davidgumberg/gtk,Distrotech/gtk2,ebassi/gtk,grubersjoe/adwaita,Lyude/gtk-,Adamovskiy/gtk,davidt/gtk,chergert/gtk,bratsche/gtk-,davidt/gtk,Adamovskiy/gtk,msteinert/gtk,Lyude/gtk-,jigpu/gtk,ebassi/gtk,jadahl/gtk,grubersjoe/adwaita,jadahl/gtk,ahodesuka/gtk,davidgumberg/gtk,alexlarsson/gtk,jessevdk/gtk,ahodesuka/gtk,jessevdk/gtk,alexlarsson/gtk,jigpu/gtk,jessevdk/gtk,Adamovskiy/gtk,Lyude/gtk-,jigpu/gtk,bratsche/gtk-,Adamovskiy/gtk,ebassi/gtk,davidgumberg/gtk,Distrotech/gtk2,Distrotech/gtk2,Adamovskiy/gtk,msteinert/gtk,Adamovskiy/gtk,alexlarsson/gtk,davidgumberg/gtk,Lyude/gtk-,jadahl/gtk,Sidnioulz/SandboxGtk,alexlarsson/gtk,msteinert/gtk,jessevdk/gtk,bratsche/gtk-,ahodesuka/gtk,davidgumberg/gtk,davidgumberg/gtk,jadahl/gtk,jessevdk/gtk,grubersjoe/adwaita,Lyude/gtk-,davidt/gtk,Sidnioulz/SandboxGtk,chergert/gtk