add trim to avoid display null as string

src/inputs/abstract.js

@@ -52,7 +52,7 @@ To create your own input you can inherit from this class.
         @param {DOMElement} element
        **/       
        value2html: function(value, element) {
-           $(element).text(value);
+           $(element).text($.trim(value));
        },
         
        /**