Fixes#1079
- Call .load() immediately after Image.open() when loading from the
on-disk cache, so OSError from corrupt/truncated files is caught
early and triggers a re-fetch from the network instead of crashing.
- Add OSError handling around image.resize() as a second safety net
for images that are corrupt after downloading.
- Replace incorrect Image_module.Palette.ADAPTIVE resampling argument
with the correct Image_module.Resampling.LANCZOS in resize().
