Fix image optimization evaluation
Fix image optimization evaluation

Don't attempt to pass data through a JPEG filter if we are unable to
filter the data.

jberkenbilt/qpdf,qpdf/qpdf,jberkenbilt/qpdf,jberkenbilt/qpdf,qpdf/qpdf,jberkenbilt/qpdf,qpdf/qpdf,qpdf/qpdf,qpdf/qpdf,jberkenbilt/qpdf