Print warning when image width or height is zero.
Print warning when image width or height is zero.

darcs-hash:20090503185724-86a4e-d75b1e75a5a1b34ce25a4f23d414bf099c362522.gz

nqv/mupdf,nqv/mupdf,nqv/mupdf,nqv/mupdf,nqv/mupdf,nqv/mupdf