Opaque / unrelated error when json file missing in HTML viewer: tlmviewer error: SyntaxError: Unexpected token '<', "

[Indivicivet]

I have the html page viewable via python -m http.server. when I try to access tlmviewer.html when there's no latest.json existing (the path I'm pointing at in my file), I get the opaque error:

tlmviewer error: SyntaxError: Unexpected token '<', "

the console error is as follows:

  | zl | @ | tlmviewer-0.0.10.js:18163
-- | -- | -- | --
  | (anonymous) | @ | tlmviewer-0.0.10.js:18173
  | __ | @ | tlmviewer-0.0.10.js:18171
  | (anonymous) | @ | tlmviewer.html:9

Uncaught (in promise) SyntaxError: Unexpected token '<', "<!DOCTYPE "... is not valid JSON
VM380:1

I would expect something like tlmviewer error: data-url "./latest.json" not found (404). hope that's helpful.