E.openFile pipe - Uncaught Error: Expecting a function to call, got Number

No problem...

Are you sure you're up to date (there should be a note in the ChangeLog about my fix) and make cleaned?

I just compiled from git master here and ran your code as-is and it works perfectly.

For debugging I'd say compile with DEBUG=1, run it under gdb and breakpoint jsExceptionHere - you can then look at the backtrace and see what really caused the error.