blockinfo: fix qemu regression in handling disk name
blockinfo: fix qemu regression in handling disk name

Regression introduced in commit 89b6284fd, due to an incorrect
conversion to the new means of converting disk names back to
the correct object.

* src/qemu/qemu_driver.c (qemuDomainGetBlockInfo): Avoid NULL deref.

siboulet/libvirt-openvz,shugaoye/libvirt,warewolf/libvirt,jeckersb/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,shugaoye/libvirt,novel/fbsd-libvirt,emaste/libvirt,shugaoye/libvirt,soulxu/libvirt-xuhj,novel/fbsd-libvirt,rlaager/libvirt,rlaager/libvirt,eskultety/libvirt,jfehlig/libvirt,jeckersb/libvirt,crobinso/libvirt,elmarco/libvirt,warewolf/libvirt,wiedi/libvirt,dumbbell/libvirt,datto/libvirt,iam-TJ/libvirt,agx/libvirt,jardasgit/libvirt,trainstack/libvirt,dumbbell/libvirt,foomango/libvirt,kantai/libvirt-vfork,eskultety/libvirt,warewolf/libvirt,leilihh/libvirt,usc-isi/libvirt,dumbbell/libvirt,andreabolognani/libvirt,jeckersb/libvirt,rmarwaha/libvirt,trainstack/libvirt,zippy2/libvirt,warewolf/libvirt,wiedi/libvirt,rmarwaha/libvirt1,kantai/libvirt-vfork,siboulet/libvirt-openvz,warewolf/libvirt,VenkatDatta/libvirt,iam-TJ/libvirt,taget/libvirt,rmarwaha/libvirt,zippy2/libvirt,emaste/libvirt,nertpinx/libvirt,eskultety/libvirt,elmarco/libvirt,usc-isi/libvirt,jardasgit/libvirt,andreabolognani/libvirt,cbosdo/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,novel/fbsd-libvirt,rlaager/libvirt,rmarwaha/libvirt1,datto/libvirt,siboulet/libvirt-openvz,iam-TJ/libvirt,shugaoye/libvirt,rmarwaha/libvirt,wiedi/libvirt,emaste/libvirt,taget/libvirt,andreabolognani/libvirt,eskultety/libvirt,datto/libvirt,jardasgit/libvirt,siboulet/libvirt-openvz,rmarwaha/libvirt1,iam-TJ/libvirt,bjzhang/libvirt,VenkatDatta/libvirt,datto/libvirt,zhlcindy/libvirt-1.1.4-maintain,agx/libvirt,kantai/libvirt-vfork,zippy2/libvirt,trainstack/libvirt,bjzhang/libvirt,foomango/libvirt,dumbbell/libvirt,VenkatDatta/libvirt,jardasgit/libvirt,trainstack/libvirt,danwent/libvirt-ovs,andreabolognani/libvirt,agx/libvirt,dumbbell/libvirt,nertpinx/libvirt,jfehlig/libvirt,elmarco/libvirt,taget/libvirt,crobinso/libvirt,usc-isi/libvirt,cbosdo/libvirt,nertpinx/libvirt,olafhering/libvirt,bjzhang/libvirt,rmarwaha/libvirt1,jeckersb/libvirt,libvirt/libvirt,leilihh/libvirt,rmarwaha/libvirt1,novel/fbsd-libvirt,trainstack/libvirt,elmarco/libvirt,foomango/libvirt,andreabolognani/libvirt,emaste/libvirt,jeckersb/libvirt,leilihh/libvirt,olafhering/libvirt,novel/fbsd-libvirt,emaste/libvirt,novel/fbsd-libvirt,eskultety/libvirt,usc-isi/libvirt,trainstack/libvirt,rmarwaha/libvirt1,usc-isi/libvirt,trainstack/libvirt,zhlcindy/libvirt-1.1.4-maintain,rlaager/libvirt,crobinso/libvirt,wiedi/libvirt,danwent/libvirt-ovs,jeckersb/libvirt,rmarwaha/libvirt,warewolf/libvirt,nertpinx/libvirt,iam-TJ/libvirt,kantai/libvirt-vfork,jfehlig/libvirt,leilihh/libvirt,elmarco/libvirt,iam-TJ/libvirt,soulxu/libvirt-xuhj,zhlcindy/libvirt-1.1.4-maintain,novel/fbsd-libvirt,VenkatDatta/libvirt,rmarwaha/libvirt,wiedi/libvirt,warewolf/libvirt,zhlcindy/libvirt-1.1.4-maintain,fabianfreyer/libvirt,soulxu/libvirt-xuhj,iam-TJ/libvirt,siboulet/libvirt-openvz,libvirt/libvirt,cbosdo/libvirt,dumbbell/libvirt,rmarwaha/libvirt,fabianfreyer/libvirt,zhlcindy/libvirt-1.1.4-maintain,soulxu/libvirt-xuhj,rlaager/libvirt,foomango/libvirt,danwent/libvirt-ovs,jeckersb/libvirt,wiedi/libvirt,cbosdo/libvirt,taget/libvirt,foomango/libvirt,fabianfreyer/libvirt,danwent/libvirt-ovs,agx/libvirt,kantai/libvirt-vfork,bjzhang/libvirt,datto/libvirt,libvirt/libvirt,emaste/libvirt,danwent/libvirt-ovs,cbosdo/libvirt,agx/libvirt,olafhering/libvirt,leilihh/libvirt,soulxu/libvirt-xuhj,zippy2/libvirt,nertpinx/libvirt,libvirt/libvirt,novel/fbsd-libvirt,wiedi/libvirt,crobinso/libvirt,taget/libvirt,novel/fbsd-libvirt,emaste/libvirt,bjzhang/libvirt,shugaoye/libvirt,olafhering/libvirt,leilihh/libvirt