chaos error causes other visualizers to remain stuck in error state

To reproduce:
1. Go to https://numberscope.colorado.edu/?name=ModFill&ver=0.4.0&rev=2334916&viz=ModFill&seq=OEIS+A001850&first=1&length=1308
2. Change visualizer to Chaos.  This will show error.
3. Change back to ModFill.  Error now.
4. Refresh modfill (soft or hard) and error goes away.