MAGETWO-59365: Countries list is not loaded if change customer website after country was selected

Author: VladimirZaets

app/code/Magento/Directory/Model/ResourceModel/Region/Collection.php

@@ -206,7 +206,7 @@ public function toOptionArray()
         if (count($options) > 0) {
             array_unshift(
                 $options,
-                ['title' => null, 'value' => null, 'label' => __('Please select a region, state or province.')]
+                ['title' => '', 'value' => '', 'label' => __('Please select a region, state or province.')]
             );
         }
         return $options;

app/code/Magento/Ui/view/base/web/js/form/element/country.js

@@ -42,6 +42,7 @@ define([
             });
 
             this.setOptions(result);
+            this.reset();
         }
     });
 });