fix previousUrl being set to current url

public/src/ajaxify.js

@@ -61,12 +61,12 @@ $(document).ready(function() {
 			apiXHR.abort();
 		}
 
-		url = ajaxify.start(url, quiet);
-
 		if (!window.location.pathname.match(/\/(403|404)$/g)) {
 			app.previousUrl = window.location.href;
 		}
 
+		url = ajaxify.start(url, quiet);
+
 		$('body').removeClass(ajaxify.data.bodyClass);
 		$('#footer, #content').removeClass('hide').addClass('ajaxifying');