Scripts assume that calling user.compare_ars(undefined) will not throw

... an exception (e.g. chat_sec.js), so return false instead.

This fixes issue #864

Thank you Accession and Nelgin for the report

exec/tests/user/except.js

@@ -4,7 +4,7 @@
 var func_list = {
 	'adjust_credits': 1,
 	'adjust_minutes': 1,
-	'compare_ars': 1,
+	'compare_ars': 0,
 	'downloaded_file': 1,
 	'get_time_left': 1,
 	'posted_message': 1,

exec/tests/user/rtypes.js

@@ -4,6 +4,7 @@ var type = {
 	'adjust_credits(0)'		: 'boolean',
 	'adjust_minutes(0)'		: 'boolean',
 	'compare_ars("")'		: 'boolean',
+	'compare_ars(undefined)'	: 'boolean',
 	'downloaded_file()'		: 'boolean',
 	'get_time_left(0)'		: 'number',
 	'posted_message(0)'		: 'boolean',

src/sbbs3/js_user.c

@@ -1074,8 +1074,10 @@ js_chk_ar(JSContext *cx, uintN argc, jsval *arglist)
 
 	if (js_argcIsInsufficient(cx, argc, 1))
 		return JS_FALSE;
-	if (js_argvIsNullOrVoid(cx, argv, 0))
-		return JS_FALSE;
+	if (JSVAL_NULL_OR_VOID(argv[0])) {
+		JS_SET_RVAL(cx, arglist, JSVAL_TRUE);
+		return JS_TRUE;
+	}
 
 	scfg = JS_GetRuntimePrivate(JS_GetRuntime(cx));