Use supplied dimensions if image load fails
Use supplied dimensions if image load fails

Modify CameraView::loadImage to test if the image load succeeded
(assuming that the bounds are all 0 on errors), and replace the old
image with an empty image (falling back on the supplied dimensions) in
case of errors.

linus-sherrill/maptk,linus-sherrill/maptk,linus-sherrill/maptk,linus-sherrill/maptk,linus-sherrill/maptk