parallels: support NULL virDomainVideoAccelDefPtr
parallels: support NULL virDomainVideoAccelDefPtr

NULL value of virDomainVideoAccelDefPtr means default
values for video acceleration, so don't report error in
this case.

Signed-off-by: Dmitry Guryanov <82bcdc4bd8b0265ee488eb5c489ce233d2f86b5c@parallels.com>

shugaoye/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,shugaoye/libvirt,elmarco/libvirt,agx/libvirt,eskultety/libvirt,nertpinx/libvirt,agx/libvirt,zippy2/libvirt,olafhering/libvirt,datto/libvirt,fabianfreyer/libvirt,olafhering/libvirt,datto/libvirt,eskultety/libvirt,crobinso/libvirt,elmarco/libvirt,jardasgit/libvirt,agx/libvirt,rlaager/libvirt,zippy2/libvirt,VenkatDatta/libvirt,eskultety/libvirt,jardasgit/libvirt,taget/libvirt,nertpinx/libvirt,jfehlig/libvirt,andreabolognani/libvirt,taget/libvirt,agx/libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,eskultety/libvirt,taget/libvirt,rlaager/libvirt,elmarco/libvirt,libvirt/libvirt,elmarco/libvirt,andreabolognani/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,nertpinx/libvirt,taget/libvirt,rlaager/libvirt,agx/libvirt,VenkatDatta/libvirt,taget/libvirt,libvirt/libvirt,nertpinx/libvirt,nertpinx/libvirt,eskultety/libvirt,crobinso/libvirt,zippy2/libvirt,libvirt/libvirt,shugaoye/libvirt,rlaager/libvirt,VenkatDatta/libvirt,datto/libvirt,olafhering/libvirt,elmarco/libvirt,jfehlig/libvirt,shugaoye/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,libvirt/libvirt,olafhering/libvirt,jardasgit/libvirt,datto/libvirt,rlaager/libvirt,jardasgit/libvirt,jardasgit/libvirt,shugaoye/libvirt,fabianfreyer/libvirt,datto/libvirt,zippy2/libvirt,crobinso/libvirt,crobinso/libvirt