util: storagefile: Tolerate NULL path when looking up volume in chain
util: storagefile: Tolerate NULL path when looking up volume in chain

chain->path may be NULL e.g. for NBD drives, so the check needs to avoid
dereferencing the path in such case

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