The "id" variable was being sporadically reset to null, and as far as
Florian and I could determine, this is actually a Spidermonkey bug.
The issue has something to do with:
1) use of "let" for the variable
2) Nesting a dynamic closure inside of a for() loop
Work around it here for now - I tried to create a minimized test case
to hand to the Spidermonkey developers, but failed. A big part of
the problem is it's only sporadically reproducible.
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