Try handle @import link errors (#2569)
Try handle @import link errors (#2569)

- Some @import resources can fail, but the style sheet can still be valid.
- Fix for https://fivethirtyeight.com/
- Fix for some websites from #2065
darkreader/darkreader,darkreader/darkreader,alexanderby/darkreader,darkreader/darkreader,alexanderby/darkreader,alexanderby/darkreader