JS error playing Swoop demo

[jdm]

joshmatthews@joshmatthews-fcmd6r servo % ./mach run -r https://playcanv.as/p/JtL2iqIH/
Powered by PlayCanvas 0.176.4 e5b7c28
[2020-04-22T15:41:20Z ERROR script::dom::bindings::error] Error at https://s3-eu-west-1.amazonaws.com/apps.playcanvas.com/R2axJfsc/playcanvas-stable.min.js:540:13 this argument is not a finite floating-point value
64 threads are still running after shutdown (bad).

[jdm]

This exception comes from

servo/components/script/dom/bindings/conversions.rs

Line 107 in d33a784

throw_type_error(cx, "this argument is not a finite floating-point value");

. The JS in question is this.source.start(0,this.startOffset%this.source.buffer.duration). this.source is an AudioBufferSourceNode, and this.source.buffer (I think) the result of decodeAudioData. Presumably either startOffset or the buffer's duration is a non-finite value, so the % calculation becomes non-finite.