qemu_blockjob: Avoid dereferencing NULL on OOM
qemu_blockjob: Avoid dereferencing NULL on OOM

Signed-off-by: Jiri Denemark <62bdf77dc47919a4d59a91822129d14633cfca81@redhat.com>

nertpinx/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,taget/libvirt,libvirt/libvirt,olafhering/libvirt,eskultety/libvirt,eskultety/libvirt,nertpinx/libvirt,libvirt/libvirt,libvirt/libvirt,eskultety/libvirt,andreabolognani/libvirt,jardasgit/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,eskultety/libvirt,datto/libvirt,crobinso/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,zippy2/libvirt,olafhering/libvirt,nertpinx/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,datto/libvirt,crobinso/libvirt,jfehlig/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,nertpinx/libvirt,zippy2/libvirt,nertpinx/libvirt,crobinso/libvirt,datto/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,crobinso/libvirt,olafhering/libvirt,taget/libvirt,jfehlig/libvirt,jardasgit/libvirt,taget/libvirt,andreabolognani/libvirt,zippy2/libvirt,jardasgit/libvirt,datto/libvirt,libvirt/libvirt,VenkatDatta/libvirt,taget/libvirt,taget/libvirt,zippy2/libvirt,olafhering/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,datto/libvirt,eskultety/libvirt