Fix #146724: Crash when deleting node group from outliner

An update to set the right context was missing after the current
`edittree` was updated.

Pull Request: https://projects.blender.org/blender/blender/pulls/147828

source/blender/editors/space_node/space_node.cc

@@ -1560,6 +1560,7 @@ static void node_id_remap(ID *old_id, ID *new_id, SpaceNode *snode)
     if (snode->treepath.last) {
       path = (bNodeTreePath *)snode->treepath.last;
       snode->edittree = path->nodetree;
+      ED_node_set_active_viewer_key(snode);
     }
     else {
       snode->edittree = nullptr;