[io] Avoid nullptr deref when printing warning in TStreamerInfo
[io] Avoid nullptr deref when printing warning in TStreamerInfo

olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root