Build environment: macOS
Moddable SDK version:

~/.jsvu/bin/xs -v
XS 16.8.1, slot 32 bytes, ID 4 bytes

Description
clearTimeout crashes:

1. on undefined
2. when called on the timeout id from that timeout callback
   In this case not clearTimeout() crashes, but internal handler -- see example 3

Case 2 is not catchable and crashes the process

Steps to Reproduce

1. ~/.jsvu/bin/xs -e 'clearTimeout(undefined)'
2. ~/.jsvu/bin/xs -e 'x=setTimeout(()=>clearTimeout(x), 100)'
3. ~/.jsvu/bin/xs -e 'x=setTimeout(()=>{clearTimeout(x);print("cleared")}, 100)'

Expected behavior
It should do nothing if there is no timeout to remove

https://www.w3.org/TR/2011/WD-html5-20110525/timers.html#dom-windowtimers-cleartimeout

If handle does not identify an entry in the list of active timeouts of the WindowTimers object on which the method was invoked, the method does nothing.