I verfied this bug with virt-viewer-2.0-17.el6.x86_64.
And virt-viewer can ignore the invalid settings and open guest correctly.
So move the bug from ON_QA to VERIFIED.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://rhn.redhat.com/errata/RHBA-2017-0587.html