[gjs] log: check that the stack is a string before converting

[Giovanni Campagna <gcampagna src gnome org>]

commit e3fdf9e3876b8a0649b88ab1672e88395a76521f
Author: Giovanni Campagna <gcampagna src gnome org>
Date:   Tue May 7 20:10:59 2013 +0200

    log: check that the stack is a string before converting
    
    gjs_string_to_utf8 goes crazy if you call it on something that is
    not on a string, and it is legitimate to call logError() with
    objects that don't have a stack (such as pure GLib.Errors)

 gjs/jsapi-util.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/gjs/jsapi-util.c b/gjs/jsapi-util.c
index de97ab5..5ba0711 100644
--- a/gjs/jsapi-util.c
+++ b/gjs/jsapi-util.c
@@ -525,7 +525,8 @@ gjs_log_exception_full(JSContext *context,
 
     if (JSVAL_IS_OBJECT(exc) &&
         gjs_object_get_property_const(context, JSVAL_TO_OBJECT(exc),
-                                      GJS_STRING_STACK, &stack))
+                                      GJS_STRING_STACK, &stack) &&
+        JSVAL_IS_STRING(stack))
         gjs_string_to_utf8(context, stack, &utf8_stack);
     else
         utf8_stack = NULL;