add exceptions to js and make invalid session access fatal + exception for a try/catch

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@5443 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/mod/languages/mod_spidermonkey/mod_spidermonkey.h

@@ -145,6 +145,7 @@ struct js_session {
 
 JSBool DEFAULT_SET_PROPERTY(JSContext * cx, JSObject *obj, jsval id, jsval *vp)
 {
+	eval_some_js("~throw new Error(\"this property cannot be changed!\");", cx, obj, vp);
 	return JS_FALSE;
 }