Revert "Workaround for #13"

This reverts commit 9a0a01d37a38cd4ad461f4ae32f598d402f7692e.
Catch and pass through errors that occur during calculation.
Scale images with both viewBox and width/height.

Previously we would not scale them if they had a viewBox, but Illustrator likes to produce ones with both a viewBox and width/height.

Fixes #13. Better version of #15, which caused other tests to fail.