[BUG] Incorrect Path pattern blocks graph tab

**Describe the bug**
When using the Neptune workbench to visualize queries if an incorrect path pattern is specified such as:

```
-p v,outv,inv
```

The results are shown but the graph tab is not available. This looks like the error is being silently swallowed by Jupyter. We should provide some sort of notification to the end user that the path pattern is wrong and then possibly ignore it when displaying the graph.

On closer investigation this appears to only be an issue when you include the edges in the path. If you change the traversal above to `g.V().outE().inV().path()` the Graph tab is not appearing for me