It's one of the two "crashing" bugs related to JavaScript and Quartz
Composer. One of the two was solved in 10.4.2 as part of
JavaScriptCore update. The other one is in Quartz Composer and I
don't know if / when we will distribute a fix - sorry :/
I'm not sure they're a way you can work around it... you can try
tweaking your JavaScript source or the number of inputs / outputs to
see if that works around the crash.