When a data-preferred-delim value is set, the list defaults to that upon initial load (for example, "-----"). When that value is null, it correctly defaults to data-default-option (i.e. "Select Country").
Seems to be happening to a script I used from v.5 also.
I'm also getting a "Cannot read property 'length' of undefined" typeerror at column 66203 on the minified js file in the for condition containing var r=0;r<n.regions.length;r++. Not sure if this is related.