core: Bail early if scaled pixbuf dimensions are zero
core: Bail early if scaled pixbuf dimensions are zero

This is possible if the input image is huge in one dimension and tiny in
the other, leading to a very small scale factor.

Signed-off-by: Philip Withnall <3ba3974e96044dcde818e6310ed799abe10671d4@tecnocode.co.uk>

pwithnall/gnome-directory-thumbnailer,pwithnall/gnome-directory-thumbnailer,GNOME/gnome-directory-thumbnailer,GNOME/gnome-directory-thumbnailer