Minor fixes to copyEncryptionParameters
Minor fixes to copyEncryptionParameters

This fixes were to code added yesterday; the problems would not have
impacted any previously released code.  These are all changes related
to the possibility that copyEncryptionParameters may be called on
behalf a different QPDF than the one being written.

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