Error in _js_exception_handler() in PHP 7

The exception handler _js_exception_handler() expects an argument of type Exception, but in php 7 most exceptions thrown are of type Error, so if an exception is thrown during the js callback, it attempts to be handled by this function, but then throws an error like Argument 1 must be an instance of Exception, instance of Error given.

In PHP 7, both Exception and Error extend Throwable, so the type hint could be changed to that, but I believe that wouldn't be compatible with pre-7. The type hint could also be removed.

See http://php.net/manual/en/function.set-exception-handler.php