ignore empty href attributes for interoperatibility with django-summernote

[czarly]

the javascript generated html code from django-summernote contains link tags without href attribute. i think this can be a general problem with javascript generated html that you integrate from third parties, so workaround this in pjaxr seems to be the right place.

[iekadou]

An empty url is a shortcut to the current URL. So a refresh button of only the pjaxr content could be a link like this <a href="">refresh</a>.

If the empty hrefs are unavoidable and are not meant to refresh the page, you could only register links with a correctly set href.

For example (i think there are more efficient css selectors for that):

$('a').not('[href=""]').on('click', function(e) {
    $(document).pjaxr.click(e);
});