Restoring previous graph leaves restore button present

## Steps to reproduce

1. Add a node to the database using query editor
```g.addV()```
2. Add new nodes to graph visualization
3. Drop new node from database
```g.V('{id}').drop()```
4. Refresh browser
5. Click restore previous graph button

## Expected results

No nodes should be added to the graph, but the restore button should disappear. Also, a warning/soft error should be shown letting the user know that a node could not be found.

Reproduce the sequence using the query editor, graph visualization, browser refresh, and the restore previous graph button. Trace the restore flow from the button entry point and verify that missing nodes are skipped, the button disappears, and a warning or soft error is shown when a node cannot be found.

Written by the indexing model from the issue text.