Perviously, if the argument to a number of bbs.* functions was not a valid
number, Synchronet would silently ignore the parameter and treat it as though
it was not specified.

The new behaviour was to use the value as a number.  However, the old code
caused the exception triggered by an inability to convert the number to
be pending until after the return (the JS_Native didn't return JS_FALSE) so
a try/catch block aorund it would not catch the exception.

The new new behaviour is to throw the exception immediately so it can be
caught and handled correctly.