KeyError: 'id' processing TypeDoc

Just tried out sphinx-js 3.1 on https://github.com/microsoft/bistring. I'm getting the following error:

Handler <function analyze at 0x7f6538653550> for event 'builder-inited' threw an exception (exception: 'id')

I patched sphinx up a bit to get this trace:

Traceback (most recent call last):
  File "/home/tavianator/.local/share/virtualenvs/docs-BrgkGiab/lib/python3.8/site-packages/sphinx/events.py", line 110, in emit
    results.append(listener.handler(self.app, *args))
  File "/home/tavianator/.local/share/virtualenvs/docs-BrgkGiab/lib/python3.8/site-packages/sphinx_js/__init__.py", line 60, in analyze
    app._sphinxjs_analyzer = analyzer.from_disk(abs_source_paths,
  File "/home/tavianator/.local/share/virtualenvs/docs-BrgkGiab/lib/python3.8/site-packages/sphinx_js/typedoc.py", line 40, in from_disk
    return cls(json, base_dir)
  File "/home/tavianator/.local/share/virtualenvs/docs-BrgkGiab/lib/python3.8/site-packages/sphinx_js/typedoc.py", line 29, in __init__
    ir_objects = self._convert_all_nodes(json)
  File "/home/tavianator/.local/share/virtualenvs/docs-BrgkGiab/lib/python3.8/site-packages/sphinx_js/typedoc.py", line 113, in _convert_all_nodes
    converted, more_todo = self._convert_node(todo.pop())
  File "/home/tavianator/.local/share/virtualenvs/docs-BrgkGiab/lib/python3.8/site-packages/sphinx_js/typedoc.py", line 160, in _convert_node
    interfaces=self._related_types(node, kind='implementedTypes'),
  File "/home/tavianator/.local/share/virtualenvs/docs-BrgkGiab/lib/python3.8/site-packages/sphinx_js/typedoc.py", line 227, in _related_types
    pathname = Pathname(make_path_segments(self._index[type['id']],
KeyError: 'id'

Which points here.

The variable type looks like this:

{'type': 'reference', 'typeArguments': [{'type': 'reference', 'name': 'String'}], 'name': 'Iterable'}

So I expect the relevant code is this line.

Start in sphinx_js/typedoc.py at _related_types and follow the _convert_node path shown in the traceback; compare the TypeDoc data from bistring.ts line 17 with the expected index entries. Reproduce against microsoft/bistring and verify that builder-inited analysis completes without KeyError.