How to fix null return value

Hi All,

Here I'm returning sysID from script include and calling that in table filler condition, but it is always showing null 

Script Include : client callable ( Glide AJAX enabled) , 
All application scopes
Roles: public

getBuisnessUnit: function() {
        var sysID = '';
        var gr = new GlideRecord('sys_user');
        gr.addQuery('sys_id', gs.getUserID());
        gr.addQuery('active', true);
        gr.query();
        if (gr.next()) {
            sysID = gr.getValue('u_business_unit');
        }
        //return sysID.toString();
		return 'ac26c204870221003ff35d88e3e3ec61';
    },

return 'ac26c204870221003ff35d88e3e3ec61'; testing Purpose just returning one sysid , even that also but still NULL value showing