storage: handle NULL return from virGetStorageVol
storage: handle NULL return from virGetStorageVol

virGetStorageVol can return NULL on out-of-memory. If it does, cleanly
abort the volume clone operation.

Signed-off-by: Michael Chapman <a17fed27eaa842282862ff7c1b9c8395a26ac320@very.puzzling.org>

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