Fix Viewer Recursion: StackOverflow in Server Setup

[lukasHoel]

This PR fixes the following bug:

Describe the bug

1. ViewerState is initialized in the trainer:

   nerfstudio/nerfstudio/engine/trainer.py

   Line 162 in 160abde

   self.viewer_state = ViewerState(

2. This eventually makes a call to parse_objects to construct the model tree:

   nerfstudio/nerfstudio/viewer/server/gui_utils.py

   Line 24 in 160abde

   def parse_object(

3. If part of the model contains an infinite recursion (e.g. a torch.nn.Module that links back to its parent for completely valid implementation reasons), then parse_objects will result in a StackOverflow since recursion is repeated indefinitely.

To Reproduce
Steps to reproduce the behavior:

1. Create a custom pipeline
2. The custom pipeline should have a torch.nn.Module with such a recursion. In my case I use torchmetrics.ClipScore, but any module with that attribute works.
3. Use the custom pipeline normally in ns-train

Expected behavior
The recursion should stop..

[tancik]

LGTM, thanks for fixing.