3D viewer cannot load larger detailed models

It looks the 3D viewer fails with larger models.

I have a model here with 10 detailed human cells. The model will load, and one can use the various controls, but the 3D viewer remains blank.
If I reduce the model to 8 cells, the 3D viewer loads.

So, we need to:

- optimize the geppetto model conversion to allow the 3d viewer to show larger models: come up with some ways to simplify the morphology if there are too many segments etc.
- when the model is too large and it cannot be shown in the 3d viewer, **we need to inform the user and not silently fail**

Data:
- Model that can be visualized: with 8 cells, no biophysics, : [HL23Net_0.001.net.nml.zip](https://github.com/MetaCell/NetPyNE-UI/files/12040175/HL23Net_0.001.net.nml.zip)
- Model that cannot be visualized: with 12 cells, no biophysics:
[HL23Net_0.001-12cells.net.nml.zip](https://github.com/MetaCell/NetPyNE-UI/files/12040350/HL23Net_0.001-12cells.net.nml.zip)

Start by loading the attached 8-cell and 12-cell models in the 3D viewer and tracing the model-conversion path when rendering remains blank. Done means larger detailed models render successfully, or the viewer clearly informs the user when a model cannot be shown instead of failing silently.

Written by the indexing model from the issue text.