IDE rendered as a blank page in macOS Safari

[Wode "Nimo" Ni]

Describe the bug

Initially reported by @keenancrane and I was able to reproduce this: https://penrose.cs.cmu.edu/try/ shows a blank page on macOS Safari v15.2 and possible above. Console shows one error without a source location:

SyntaxError: Invalid regular expression: invalid group specifier name

In local development, same thing but no console error at all.