Error !

IndexError: list index out of range

<title><![CDATA[${object.val('title')} ]]></title><link>${site.REQUEST['SERVER_URL']}${object.url()}</link> <description><![CDATA[]]></description> <language>no</language> <pubDate>${format_date(datetime.fromtimestamp(myobj[0].publishDate(returnType=1)))}</pubDate> <generator>Lime CMS 4</generator> <copyright>${site.val('title')}</copyright> <managingEditor>global@global.no</managingEditor> <atom:link href="${site.REQUEST['SERVER_URL']}${object.url()}" rel="self" type="application/rss+xml" />
templates/global/rss, line 55:
<pubDate>${format_date(datetime.fromtimestamp(myobj[0].publishDate(returnType=1)))}</pubDate>
/srv/globalnodata/limecms/global/global01/local/lib/python2.7/site-packages/Mako-1.0.2-py2.7.egg/mako/runtime.py, line 890:
callable_(context, *args, **kwargs)
/srv/globalnodata/limecms/global/global01/local/lib/python2.7/site-packages/Mako-1.0.2-py2.7.egg/mako/runtime.py, line 864:
_exec_template(inherit, lclcontext, args=args, kwargs=kwargs)
/srv/globalnodata/limecms/global/global01/local/lib/python2.7/site-packages/Mako-1.0.2-py2.7.egg/mako/runtime.py, line 829:
**_kwargs_for_callable(callable_, data))
/srv/globalnodata/limecms/global/global01/local/lib/python2.7/site-packages/Mako-1.0.2-py2.7.egg/mako/template.py, line 445:
return runtime._render(self, self.callable_, args, data)
/var/limecms/global/global01/global-inst-02/Products/LimeTemplate/LimeTemplate.py, line 702:
html = mytemplate.render(object=object, site=site, request=self.REQUEST, extra=extra.get('kwargs', None), **extra)